Parameter Name	FORTRAN Type	Default Value	Explanation
approximation	C*20	'boussinesq'	Parameter to choose the approximation of the model equations. Currently two approximations are available: 'boussinesq' The Boussinesq approximation assumes an incompressible fluid. The density is assumed to be spatially and temporally constant. Internally the density is set to 1 kg/m3. 'anelastic' The anelastic approximation allows for a density decrease with height. The density is however still horizontally and temporally constant. The vertical profile of the density is computed based on the surfaces_pressure and the vertical profile of the potential temperature. The anelastic approximation requires momentum_advec = "ws-scheme". Furthermore, conserve_volume_flow = .TRUE. is not supported. Note, that the default flux representation for input and output depends on the approximation. For details, please see flux_input_mode and flux_output_mode.
cloud_physics	L	.F.	Parameter to switch on the condensation scheme. For cloud_physics = .T., equations for the total water content and the liquid water potential temperature are solved instead of those for specific humidity and potential temperature. The parameterization of cloud and precipitation physics can be steered with cloud_scheme. Also, cloud-top cooling by longwave radiation can be utilized (see cloud_top_radiation). cloud_physics = .T. requires humidity = .T.. This condensation scheme is not allowed if cloud droplets are simulated explicitly (see cloud_droplets).
cloud_scheme	C*20	'saturation_adjust'	Parameter to choose microphysics for bulk cloud physics (which requires cloud_physics = .TRUE.). The following values are allowed: 'saturation_adjust' Simple saturation adjustment scheme (also known as 0%-or100% scheme), in which a grid volume is either saturated or subsaturated. Detailed information about the condensation scheme is given in the description of the cloud physics module? (pdf-file). Supersaturations are instantaneously condensed to liquid water. No precipitation is produced. If precipitation is important, use 'kessler or 'seifert_beheng'. 'kessler' One-moment cloud microphysics according to Kessler (1969). It is also based on the saturation adjustment scheme to diagnose cloud water. However, it allows precipitation if the liquid cloud water exceeds a threshold value. This water is instantaneously removed from the model domain. Additionally, liquid cloud water is allowed to sediment if cloud_water_sedimentation is set to true. 'seifert_beheng' Two-moment cloud microphysics according to Seifert and Beheng (2006). It is also based on the saturation adjustment scheme to diagnose cloud water. The cloud drop number concentration is set via nc_const. Rain water and hence precipitation is treated with two additional prognostic equations for rain water content and rain drop concentration, including autoconversion, accretion, selfcollection, breakup, evaporation, and sedimentation. Ventilation effect on evaporation is steered by ventilation_effect and set to true per default. Sedimentation can be controlled via c_sedimentation, limiter_sedimentation. Turbulence effects on accretion and autoconversion are steered via collision_turbulence. Additionally, liquid cloud water is allowed to sediment too if cloud_water_sedimentation is set to true. 'morrison' Two-moment cloud microphysics according to Seifert and Beheng (2006), Khairoutdinov and Kogan (2000), Khvorostynaov and Curry (2006) and Morrison and Grabowski (2007). The 'morrison'-scheme can be understood as an extension of the implemented 'seifert_beheng'-scheme. In comparison to the 'seifert_beheng'-scheme there are three main differences. First, instead of saturation adjustment the diffusional growth is parametrized while calculating condensation/evaporation rates. Second, the activation is considered with a simple Twomey activation-scheme. For this also Koehler-theory can take into account with the parameter curvature_solution_effects_bulk = T. The background aerosol concentration, which also determines the maximum number of activated cloud droplets, can be prescribed with na_init. Thirdly, the number concentration of cloud droplets (nc) and the cloud water content (qc) are prognostic quantities. This allows a change of the cloud droplet number which is also considered for all microphysical processes.
cloud_top_radiation	L	.F.	(until r1496 this parameter was named radiation). Parameter to switch on longwave radiation cooling at cloud-tops. Long-wave radiation processes are parameterized by the effective emissivity, which considers only the absorption and emission of long-wave radiation at cloud droplets. The radiation scheme can be used only with cloud_physics = .T..
conserve_volume_flow	L	.F.	Conservation of volume flow in x- and y-direction. In case of lateral cyclic boundary conditions (bc_lr = 'cyclic' and bc_ns = 'cyclic`'`) conserve_volume_flow = .T. guarantees that the volume flow through the xz- and yz-cross-sections of the total model domain remains constant throughout the run depending on the chosen conserve_volume_flow_mode. In case of non-cyclic lateral boundary conditions (bc_lr /= 'cyclic' or bc_ns /= 'cyclic`'`) this option guarantees that the volume flow at the inflow boundary equals at each time step the volume flow at the outflow. Note that conserve_volume_flow = .T. requires dp_external = .F.. In case of non-cyclic lateral boundary conditions, detailed information about the conservation of volume flow can be found in the documentation.
conserve_volume_flow_mode	C*16	'default'	Mode of volume flow conservation. The following values are allowed: 'default' Per default, PALM uses 'initial_profiles' . 'initial_profiles' The target volume flow is calculated at t=0 from the initial profiles of u and v. This option is also standard for non-cyclic lateral boundary conditions (bc_lr /= 'cyclic' or bc_ns /= 'cyclic`'`) because the (spanwise averaged) inflow profiles do not vary with time and are identical with the initial profiles. 'inflow_profile' The target volume flow is calculated at every time step from the inflow profile of u or v, respectively. This setting is only allowed for non-cyclic lateral boundary conditions (bc_lr /= 'cyclic' or bc_ns /= 'cyclic`'`). This option is not implemented so far, because at this time (spanwise averaged) inflow profiles do not vary with time in the standard code. 'bulk_velocity' The target volume flow is calculated from a predefined bulk velocity (see u_bulk and v_bulk). This setting is only allowed for cyclic lateral boundary conditions . Note that conserve_volume_flow_mode only comes into effect if conserve_volume_flow = .T..
coupling_start_time	R	0.0	Simulation time of precursor run. Sets the time period a precursor run shall run uncoupled. This parameter is used to set up the precursor run control for atmosphere-ocean-coupled runs. It has to be set individually to the atmospheric / oceanic precursor run. The time in the data output will show negative values during the precursor run. See coupled runs for further information.
dp_external	L	.F.	External pressure gradient switch. This parameter is used to switch on/off an external pressure gradient as driving force. The external pressure gradient is controlled by the parameters dp_smooth, dp_level_b and dpdxy. Note that dp_external = .T. requires conserve_volume_flow = .F.. It is normally recommended to disable the Coriolis force by setting omega = 0.0.
dp_smooth	L	.F.	Vertically smooth the external pressure gradient using a sinusoidal smoothing function. This parameter only applies if dp_external = .T.. It is useful in combination with dp_level_b >> 0 to generate a non-accelerated boundary layer well below dp_level_b.
dp_level_b	R	0.0	Lower limit of the vertical range for which the external pressure gradient is applied (in m). This parameter only applies if dp_external = .T.. It must hold the condition zu(0) <= dp_level_b <= zu(nzt). It can be used in combination with dp_smooth = .T. to generate a non-accelerated boundary layer well below dp_level_b if dp_level_b >> 0. Note that there is no upper limit of the vertical range because the external pressure gradient is always applied up to the top of the model domain.
dpdxy	R(2)	2 * 0.0	Values of the external pressure gradient applied in x- and y-direction, respectively (in Pa/m). This parameter only applies if dp_external = .T.. It sets the pressure gradient values. Negative values mean an acceleration, positive values mean deceleration. For example, dpdxy = -0.0002, 0.0, drives the flow in positive x-direction.
e_init	R	0.0	Initial subgrid-scale TKE in m²s^-2. This option prescribes an initial subgrid-scale TKE from which the initial diffusion coefficients K_m and K_h will be calculated if e_init is positive. This option only has an effect if km_constant is not set.
e_min	R	0.0	Minimum subgrid-scale TKE in m²s^-2. This option adds artificial viscosity to the flow by ensuring that the subgrid-scale TKE does not fall below the minimum threshold e_min.
flux_input_mode	C*40	'approximation-specific'	Parameter to choose the flux unit for input data. Currently three choices are available: 'kinematic' The flux input data is assumed to be given as kinematic fluxes with the unit K m/s for sensible heat fluxes, kg/kg m/s for latent heat fluxes and m2/s2 for momentum fluxes. 'dynamic' The flux input data is assumed to be given as dynamic fluxes with the unit W/m2 for sensible and latent heat fluxes and N/m2 for momentum fluxes. 'approximation-specific' The flux input representation is chosen depending on the approximation. For approximation = "boussinesq" the fluxes are represented as "kinematic". For approximation = "anelastic" the fluxes are represented as "dynamic".
flux_output_mode	C*40	'approximation-specific'	Parameter to choose the flux unit for output data. Currently three choices are available: 'kinematic' The flux output data is given as kinematic fluxes with the unit K m/s for sensible heat fluxes, kg/kg m/s for latent heat fluxes and m2/s2 for momentum fluxes. 'dynamic' The flux output data is given as dynamic fluxes with the unit W/m2 for sensible and latent heat fluxes and N/m2 for momentum fluxes. 'approximation-specific' The flux output representation is chosen depending on the approximation. For approximation = "boussinesq" the fluxes are represented as "kinematic". For approximation = "anelastic" the fluxes are represented as "dynamic".
galilei_transformation	L	.F.	Application of a Galilei-transformation to the coordinate system of the model. With galilei_transformation = .T., a so-called Galilei-transformation is switched on which ensures that the coordinate system of the model is moved along with the geostrophic wind. Alternatively, the model domain can be moved along with the averaged horizontal wind (see use_ug_for_galilei_tr, this can and will naturally change in time). With this method, numerical inaccuracies of the Piacsek - Williams - scheme (concerns, in particular, the momentum advection) are minimized. Beyond that, in the majority of cases, the lower relative velocities in the moved system permit a larger time step (dt). Switching the transformation on is only worthwhile if the geostrophic wind (ug, vg) and the averaged horizontal wind clearly deviate from the value 0. In each case, the distance the coordinate system has been moved is written to the file RUN_CONTROL. Non-cyclic lateral boundary conditions (see bc_lr and bc_ns), the specification of a geostrophic wind that is not constant with height as well as e.g. stationary inhomogeneities at the bottom boundary do not allow the use of this transformation.
humidity	L	.F.	Parameter to switch on the prognostic equation for specific humidity q. The initial vertical profile of q can be set via parameters q_surface, q_vertical_gradient and q_vertical_gradient_level. Boundary conditions can be set via q_surface_initial_change and surface_waterflux. If the condensation scheme is switched on (cloud_physics = .T.), q becomes the total liquid water content (sum of specific humidity and liquid water content).
km_constant	R	variable (computed from TKE)	Constant eddy diffusivities are used (laminar simulations). If this parameter is specified, both in the 1d and in the 3d-model constant values for the eddy diffusivities are used in space and time with K_m = km_constant and K_h = K_m / prandtl_number. The prognostic equation for the subgrid-scale TKE is switched off. Constant eddy diffusivities are only allowed with the constant flux layer (constant_flux_layer) switched off.
large_scale_forcing	L	.F.	Parameter to choose large-scale forcing from an external file. By means of large_scale_forcing = .T. the time-dependent surface heat flux shf, surface water flux qsws, surface temperature pt_surface, surface humidity and surface pressure surface_pressure as well as vertical profiles of the geostrophic wind components ug and vg, the large-scale vertical subsidence profile w_subs, the horizontal large-scale advection tendencies of temperature td_lsa_lpt and humidity td_lsa_q and the large-scale subsidence tendencies of temperature td_sub_lpt and humidity td_sub_q are provided in the simulation. An example can be found here. large_scale_forcing = .T. requires humidity = .T.. It is not implemented for ocean runs, and it does also not work for non-cyclic lateral boundary conditions and non-flat topography. It is possible to drive the simulations either by means of surface fluxes or by means of prescribed surface values for temperature and humidity. In case of simulating moderately tall buildings on otherwise flat terrain, the user might choose to nevertheless apply large_scale_forcing. This can be done by setting lsf_exception = .T.. However, it has not been tested so far and thus should be handled with care. If large_scale_forcing = .T., the input file LSF_DATA is required. This file has to contain two kinds of information: time-dependent surface values and time-dependent profile information which can be provided by measurements or larger scale models. In case large-scale forcing shall be used without nudging (nudging = .F.) initial profiles of potential temperature, humidity, and horizontal wind components have to be provided by means of pt_surface, pt_vertical_gradient, pt_vertical_gradient_level and so forth.
large_scale_subsidence	L	.F.	Parameter to enable large-scale subsidence/ascent for atmospheric simulations. With large_scale_subsidence = .T., an additional tendency term, tend_subs, is calculated for the scalar quantities, e.g. for potential temperature it is tend_subs(k,j,i) = - w_subs(k)* dpt(k,j,i) / dz. The profile for the subsidence velocity w_subs can either be set via subs_vertical_gradient and subs_vertical_gradient_level or by reading it from the large-scale forcing data set LSF_DATA. If use_subsidence_tendencies is set to .T., the subsidence velocity w_subs is not used. Instead, subsidence tendencies for temperature and humidity are read in from the large-scale forcing data set LSF_DATA and applied to the prognostic variables in the subroutine `ls_advec`. large_scale_subsidence is not implemented for ocean runs. Attention: The large-scale vertical motion is only applied to the prognostic equation for the scalar quantities (potential temperature, humidity if humidity = .T. or passive scalar if passive_scalar = .T.). It should not be applied to the momentum equations due to incompressibility. Applying it also to the horizontal velocity components would result in mass inconsistencies.
lsf_exception	L	.F.	Parameter to explicitly allow large-scale forcing in case of topography /= 'flat' . So far, large_scale_forcing is not implemented to be used together with topography. However, in case of simulating moderately tall buildings on otherwise flat terrain, the user might choose to nevertheless apply large_scale_forcing. This can be done by setting lsf_exception = .T.. Attention: This has not been tested so far and thus should be handled with care.
neutral	L	.F.	Parameter to switch off calculation of temperature equation. For simulating flows with pure neutral stratification, solving the temperature equation can be switched off with neutral = .T. in order to save CPU time. Additionally, this will also switch off the calculation of all buoyancy related terms. In case of neutral = .T. non-zero values for parameters surface_heatflux and top_heatflux are not allowed.
nudging	L	.F.	Parameter to choose nudging. Nudging is a relaxation technique which adjusts the large-eddy simulation to a given, larger scale flow situation. It can, for example, be used to simulate an observed situation. Further information can be found here. With nudging = .T., additional tendencies are calculated for the prognostic variable u, v, pt, and q. It requires humidity = .T. as well as large_scale forcing = .T.. So far, it is not implemented for ocean runs and non-cyclic lateral boundary conditions. An example can be found here. Additionally, if nudging is set to .T., the input file NUDGING_DATA. This file contains profile information at several time steps about the relaxation time scale tau and the prognostic variables u, v, w, pt, q which must be provided by a larger scale model or by measurements.
ocean	L	.F.	Parameter to switch on ocean runs. By default PALM is configured to simulate atmospheric flows. However, starting from version 3.3, ocean = .T. allows simulation of ocean turbulent flows. Setting this switch has several effects: An additional prognostic equation for salinity is solved. The potential temperature in buoyancy and stability-related terms is replaced by potential density. Potential density is calculated from the equation of state for seawater after each time step, using the algorithm proposed by Jackett et al. (2006, J. Atmos. Oceanic Technol., 23, 1709-1728). So far, only the initial hydrostatic pressure is entered into this equation. z=0 (sea surface) is assumed at the model top (vertical grid index k=nzt on the w-grid), with negative values of z indicating the depth. Initial profiles are constructed (e.g. from pt_vertical_gradient / pt_vertical_gradient_level) starting from the sea surface, using surface values given by pt_surface, sa_surface, ug_surface, and vg_surface. Zero salinity flux is used as default boundary condition at the bottom of the sea. If switched on, random perturbations are by default imposed to the upper model domain from zu(nzt*2/3) to zu(nzt-3). Relevant parameters to be exclusively used for steering ocean runs are bc_sa_t, bottom_salinityflux, sa_surface, sa_vertical_gradient, sa_vertical_gradient_level, and top_salinityflux. Section 4.4.2? gives an example for appropriate settings of these and other parameters necessary for ocean runs.
passive_scalar	L	.F.	Parameter to switch on the prognostic equation for a passive scalar. The initial vertical profile of s can be set via parameters s_surface, s_vertical_gradient and s_vertical_gradient_level. Boundary conditions can be set via s_surface_initial_change and surface_scalarflux.
pt_reference	R	value of pt_surface	Reference temperature to be used in the buoyancy term (in K). This parameter only becomes effective if reference_state = 'single_value' has been chosen for the reference state to be used in the buoyancy term. Attention: This parameter has no effect in case of ocean runs (see ocean), where potential density is used in the buoyancy term (see reference_state for more details).
random_heatflux	L	.F.	Parameter to impose random perturbations on the internal two-dimensional near surface heat flux field shf. If a near surface heat flux is used as a bottom boundary condition (see surface_heatflux), it is by default assumed to be horizontally homogeneous. Random perturbations can be imposed on the internal two-dimensional heat flux field shf by assigning random_heatflux = .T.. The disturbed heat flux field is calculated by multiplying the values at each mesh point with a normally distributed random number with a mean value and standard deviation of 1. This is repeated after every time step. In case of a non-flat topography, assigning random_heatflux = .T. imposes random perturbations on the combined heat flux field shf composed of surface_heatflux at the bottom surface and wall_heatflux(0) at the topography top face.
reference_state	C*20	'initial_profile'	This parameter defines what is used as reference state in the buoyancy term. There are three options: 'initial_profile' The initial vertical potential temperature profile will be used. See pt_surface and pt_vertical_gradient for how to set the initial profile. In case of runs with humidity, the virtual potential temperature will be used instead (see q_surface and q_vertical_gradient for how to set the initial specific humidity profile). In ocean runs, potential density is used instead of temperature (calculated from the initial potential temperature and salinity profile, see sa_surface and sa_vertical_gradient for how to set the initial salinity profile). In case of initializing_actions= 'cyclic_fill', the main run uses the initial profile of the precursor run. 'horizontal_average' The instantaneous horizontally averaged potential temperature profile will be used. Please be aware that this causes the reference state to change in time. In case of runs with humidity, the virtual potential temperature will be used instead. In ocean runs, potential density is used. 'single_value' A constant single potential temperature value is used as reference state. The respective value can be defined with parameter pt_reference. Warning: In case of runs with humidity, the virtual potential temperature is used. The reference value is then calculated from pt_reference and the surface specific humidity (see q_surface), i.e. it cannot be explicitly set by the user. In ocean runs, the reference value cannot be explicitly set by the user. Instead, it is calculated as the vertical average of the initial potential density profile.
subs_vertical_gradient	R(10)	10 * 0.0	Gradient(s) of the profile for the large-scale subsidence/ascent velocity (in (m/s) / 100 m). This gradient holds starting from the height level defined by subs_vertical_gradient_level (precisely: for all uv levels k where zu(k) > subs_vertical_gradient_level, w_subs(k) is set: w_subs(k) = w_subs(k-1) + dzu(k) * subs_vertical_gradient) up to the top boundary or up to the next height level defined by subs_vertical_gradient_level. A total of 10 different gradients for 11 height intervals (10 intervals if subs_vertical_gradient_level(1) = 0.0) can be assigned. Example: subs_vertical_gradient = -0.002, 0.0, subs_vertical_gradient_level = 0.0, 1000.0, That defines the subsidence/ascent profile to be linear up to z = 1000.0 m with a surface value of 0 m/s. Due to the gradient of -0.002 (m/s) / 100 m the subsidence velocity has a value of -0.02 m/s in z = 1000.0 m. For z > 1000.0 m up to the top boundary the gradient is 0.0 (m/s) / 100 m (it is assumed that the assigned height levels correspond with uv levels). This results in a subsidence velocity of -0.02 m/s at the top boundary. With an appropriate construction of w_subs, the height of the boundary layer z_i can be kept approximately constant.
subs_vertical_gradient_level	R(10)	10 * 0.0	Height level from which on the gradient for the subsidence/ascent velocity defined by subs_vertical_gradient is effective (in m). The height levels have to be assigned in ascending order. The default values result in a profile which is zero everywhere regardless of the values of subs_vertical_gradient. For the piecewise construction of the subsidence/ascent velocity profile see subs_vertical_gradient.
u_bulk	R	0.0	u-component of the predefined bulk velocity (in m/s). This parameter comes into effect if conserve_volume_flow = .T. and conserve_volume_flow_mode = 'bulk_velocity'.
use_subsidence_tendencies	L	.F.	This control parameter determines how the large-scale subsidence is computed for runs with large-scale forcing. If it is set to .F., the large-scale subsidence velocity w_subs is used to advect the prognostic variables (subroutine `subsidence`). If it is set to .T., the subroutine `subsidence` is not called and the subsidence tendencies from LSF_DATA are applied to the prognostic variables in the new subroutine `ls_advec`. The usage of use_subsidence_tendencies requires large_scale_forcing = .T. as well as large_scale_subsidence = .T..
use_ug_for_galilei_tr	L	.T.	Switch to determine the translation velocity in case that a Galilean transformation is used. In case of a Galilean transformation (see galilei_transformation), use_ug_for_galilei_tr = .T. ensures that the coordinate system is translated with the geostrophic windspeed. Alternatively, with use_ug_for_galilei_tr = .F., the geostrophic wind can be replaced as translation speed by the (volume) averaged velocity. However, in this case, the user must be aware of fast growing gravity waves, so this choice is usually not recommended!
v_bulk	R	0.0	v-component of the predefined bulk velocity (in m/s). This parameter comes into effect if conserve_volume_flow = .T. and conserve_volume_flow_mode = 'bulk_velocity'.

Grid:

Parameter Name	FORTRAN Type	Default Value	Explanation
dx	R	1.0	Horizontal grid spacing along the x-direction (in m). Along x-direction, only a constant grid spacing is allowed. For coupled runs (see details) the product of dx and nx in both parameter files PARIN and PARIN_O has to be the same (same model domain length in x-direction).
dy	R	1.0	Horizontal grid spacing along the y-direction (in m). Along y-direction, only a constant grid spacing is allowed. For coupled runs (see details) the product of dy and ny in both parameter files PARIN and PARIN_O has to be the same (same model domain length in y-direction).
dz	R		Vertical grid spacing (in m). This parameter must be assigned by the user because no default value is given. By default, the model uses constant grid spacing along the z-direction, but it can be stretched using the parameters dz_stretch_level and dz_stretch_factor. In case of stretching, a maximum allowed grid spacing can be given by dz_max. Assuming a constant dz, the scalar levels (zu) are calculated directly by: zu(0) = - dz * 0.5 zu(1) = dz * 0.5 The w-levels lie half between them: zw(k) = ( zu(k) + zu(k+1) ) * 0.5
dz_max	R	9999999.9	Allowed maximum vertical grid spacing (in m). If the vertical grid is stretched (see dz_stretch_factor and dz_stretch_level), dz_max can be used to limit the vertical grid spacing. Attention: So far, vertical grid stretching cannot be applied when simultaneously using PALM's particle model (see list of Particle Parameters).
dz_stretch_factor	R	1.08	Stretch factor for a vertically stretched grid (see dz_stretch_level). The stretch factor should not exceed a value of approx. 1.10 - 1.12, otherwise the discretization errors due to the stretched grid are not negligible anymore. (refer Kalnay de Rivas)
dz_stretch_level	R	100000.0	Height level above/below which the grid is to be stretched vertically (in m). For ocean = .F., dz_stretch_level is the height level (in m) above which the grid is to be stretched vertically. The vertical grid spacings dz above this level are calculated as dz(k+1) = dz(k) * dz_stretch_factor and used as spacings for the scalar levels (zu). The w-levels are then defined as: zw(k) = ( zu(k) + zu(k+1) ) * 0.5. For ocean = .T., dz_stretch_level is the height level (in m, negative) below which the grid is to be stretched vertically. The vertical grid spacings dz below this level are calculated correspondingly as dz(k-1) = dz(k) * dz_stretch_factor. Attention: So far, vertical grid stretching cannot be applied when simultaneously using PALM's particle model (see list of Particle Parameters).
nx	I		Number of grid points in x-direction. A value for this parameter must be assigned. Since the lower array bound in PALM starts with i = 0, the actual number of grid points is equal to nx+1. In case of cyclic boundary conditions along x, the domain size is (nx+1)* dx. For parallel runs nx+1 must be an integral multiple of the number of processors (see npex and npey) along x- as well as along y-direction (due to data transposition restrictions). For coupled runs (see details) the product of dx and nx in both parameter files PARIN and PARIN_O has to be same (same model domain length in x-direction).
ny	I		Number of grid points in y-direction. A value for this parameter must be assigned. Since the lower array bound in PALM starts with j = 0, the actual number of grid points is equal to ny+1. In case of cyclic boundary conditions along y, the domain size is (ny+1) * dy. For parallel runs ny+1 must be an integral multiple of the number of processors (see npex and npey) along y- as well as along x-direction (due to data transposition restrictions). For coupled runs (see details) the product of dy and ny in both parameter files PARIN and PARIN_O has to be same (same model domain length in y-direction).
nz	I		Number of grid points in z-direction. A value for this parameter must be assigned. Since the lower array bound in PALM starts with k = 0 and since one additional grid point is added at the top boundary (k = nz+1), the actual number of grid points is nz+2. However, the prognostic equations are only solved up to nz (u, v, scalar quantities) or up to nz-1 (w). The top boundary for u, v and scalar quantities is at k = nz+1 (u, v) while at k = nz for w. For parallel runs, nz must be an integral multiple of the number of processors in x-direction (due to data transposition restrictions).

Numerics:

Parameter Name	FORTRAN Type	Default Value	Explanation
call_psolver_at_all_substeps	L	.T.	Switch to steer the call of the pressure solver. In order to speed-up performance, the Poisson equation for perturbation pressure (see psolver) can be called only at the last substep of multistep Runge-Kutta time step schemes (see timestep_scheme) by setting call_psolver_at_all_substeps = .F.. In many cases, this sufficiently reduces the divergence of the velocity field. Nevertheless, small-scale ripples (2-delta-x) may occur. In this case and in case of non-cyclic lateral boundary conditions, the default value call_psolver_at_all_substeps = .T. should be used. Pressure solver must be called at each RK3 substep when momentum_advec = 'ws-scheme'.
cfl_factor	R	0.1, 0.8 or 0.9 (see right)	Time step limiting factor. In the model, the maximum allowed time step according to CFL and diffusion-criterion dt_max is reduced by dt = dt_max * cfl_factor in order to avoid stability problems which may arise in the vicinity of the maximum allowed time step. The condition 0.0 < cfl_factor < 1.0 applies. The default value of cfl_factor depends on the timestep_scheme used: For the third order Runge-Kutta scheme it is cfl_factor = 0.9., for the second-order Runge-Kutta scheme a value of 0.8 is applied. The default value for the Euler scheme is cfl_factor = 0.9.
collective_wait	L	see right	Set barriers in front of collective MPI operations. Depending on the communication network in use, setting of barriers (MPI_BARRIER) in front of collective MPI operations (MPI_ALLTOALL, MPI_ALLREDUCE) may speed up the code, e.g. by a few percent on SGI-ICE-systems with Infiniband fat tree, but only for a larger number of PEs (>= 2048) and if dual rail mode is switched on (default on SGI-systems at HLRN). Therefore, `collective_wait` is `.TRUE.` by default on SGI-systems (if hostname(3:5) = "`sgi`", given with mrun-option `-h`), but `.FALSE.` on all other systems.
cycle_mg	C*1	'w'	Type of cycle to be used with the multigrid method. This parameter determines which type of cycle is applied in the multigrid method used for solving the Poisson equation for perturbation pressure (see psolver). It defines in which way it is switched between the fine and coarse grids. So-called v- and w-cycles are realized (i.e. cycle_mg may be assigned the values 'v' or 'w' ). The computational cost of w-cycles is much higher than that of v-cycles, however, w-cycles give a much better convergence.
fft_method	C*20	'system-specific'	FFT-method to be used. The fast Fourier transformation (FFT) is used for solving the perturbation pressure equation with a direct method (see psolver) and for calculating power spectra (see optional software packages?). By default, system-specific, optimized routines from external vendor libraries are used. However, these are available only on certain computers and there are sometimes more or less severe restrictions concerning the number of grid points to be used with them. There are two other PALM internal methods available on every machine (their respective source code is part of the PALM source code): 1.: The Temperton-method from Clive Temperton (ECMWF) which is computationally very fast and switched on with fft_method = 'temperton-algorithm'. The number of horizontal grid points (nx+1, ny+1) to be used with this method must be composed of prime factors 2, 3 and 5. 2.: The Singleton-method which is very slow but has no restrictions concerning the number of grid points to be used with, switched on with fft_method = 'singleton-algorithm'. Furthermore, the fftw (see http://www.fftw.org ) can be used by setting fft_method = 'fftw' . This also requires to set the cpp-preprocessor switch `-D__fftw` in the `%cpp_options`-line of the configuration file, and to give the paths to the respective fftw include file and library by a `%fftw_inc` and `%fftw_lib` line, respectively. The fftw-routines are more than two times faster than the Temperton-fft.
loop_optimization	C*16	see right	Method used to optimize loops for solving the prognostic equations. By default, the optimization method depends on the host on which PALM is running. On machines with vector-type CPUs, single 3d-loops are used to calculate each tendency term of each prognostic equation, while on all other machines, all prognostic equations are solved within one big loop over the two horizontal indices `i` and `j` (giving a good cache utilization). The default behavior can be changed by setting either loop_optimization = 'vector' or loop_optimization = 'cache'.
masking_method	L	.F.	Switch for topography boundary conditions in 'multigrid_noopt' solver. By default, Neumann boundary conditions for perturbation pressure are used in the multigrid solver at all wall boundaries. In case of masking_method = .TRUE., the masking method is used instead (i.e. the solver runs through the topography). Note: masking_method has only an effect if psolver = 'multigrid_noopt', otherwise, if psolver = 'multigrid', masking is always used, so that setting masking_method has no effect on the simulation at all. Moreover, if you use older revisions (<1931), it is noted that the naming convention for the multigrid solvers was different, 'multigrid_noopt' (now) was 'multigrid' (<1931), and 'multigrid' (now) was 'multigrid_fast' (<1931). Warning: In case of complex topography and masking_method = .FALSE., the wind velocity may possibly blow up at certain grid points. Hence, so far it is recommended to use masking_method = .TRUE. in case psolver = 'multigrid_noopt'.
mg_cycles	I	-1	Number of cycles to be used with the multigrid scheme. This parameter determines the number of cycles to be carried out in the multigrid method used for solving the Poisson equation for perturbation pressure (see psolver). The type of the cycles can be set with cycle_mg. By default (mg_cyles = -1), the number of cycles depends on the requested accuracy of the scheme (see residual_limit) and may vary from time step to time step. In this case, the CPU time for a run will be difficult to estimate since it heavily depends on the total number of the cycles to be carried out. By assigning mg_cycles a value (>= 1), the number of cycles can be fixed so that the CPU time can be clearly estimated. Note: When using a fixed number of cycles, the user must examine the local file RUN_CONTROL regularly to check whether the divergence of the velocity field is sufficiently reduced by the pressure solver. It should be reduced at least by two orders of magnitude. For cyclic boundary conditions along both horizontal directions (see bc_lr and bc_ns) mg_cycles = 2 is typically a good choice, for non-cyclic lateral boundary conditions mg_cycles = 4 may be sufficient.
mg_switch_to_pe0_level	I	-1	Grid level at which data shall be gathered on PE0. In case of a run using several PEs and the multigrid method for solving the Poisson equation for perturbation pressure (see psolver), the value of this parameter defines on which grid level the data are gathered on PE0 in order to allow for a further coarsening of the grid. The finest grid defines the largest grid level. If mg_switch_to_pe0_level = 0, the gathering level is determined automatically and displayed in file RUN_CONTROL. It is only possible to gather data from a level larger than the one determined automatically. A test run may be necessary to determine this level. Default setting is mg_switch_to_pe0_level = -1, which prevents that data are collected on PE0 at all, i.e. coarsening of grids is limited by the subdomains. Remark: The default setting is significantly faster compared to automatically determining or explicitly prescribing mg_switch_to_pe0_level. Even though the divergence reduction of the multigrid solver is slightly smaller with the default setting, gathering on PE0 does not justify the additional cost so far.
momentum_advec	C*10	'ws-scheme'	Advection scheme to be used for the momentum equations. The user can choose between the following schemes: 'ws-scheme' The 5th order upwind scheme of Wicker and Skamarock (2002, Mon. Wea. Rev, 130, 2088-2097) is used. The dispersion error is much smaller than the dispersion error of 'pw-scheme' . The 5th order scheme implies a small numerical dissipation that stabilizes the solution. To assure a stable numerical solution the time integration has to be carried out with timestep_scheme = 'runge-kutta-3' . This scheme is based on a formulation of the advection term in flux form, which requires a vanishing divergence of the flow field, else a stable numerical solution is not given. So call_psolver_at_all_substeps = .T. has to be used. Note: Due to the larger stencil of this scheme vertical grid stretching should be handled with care. The computation of turbulent fluxes takes place inside the advection routines to get a statistical evaluation consistent to the numerical solution. Important: The number of ghost layers for 2d and 3d arrays changed. This affects also the user interface. Please adapt the allocation of 2d and 3d arrays in your user interface like here. Furthermore, the exchange of ghost layers for 3d variables changed, so calls of exchange_horiz in the user interface have to be modified. Here an example for the u-component of the velocity: CALL exchange_horiz( u , nbgp ). 'pw-scheme' The scheme of Piacsek and Williams (1970, J. Comp. Phys., 6, 392-405) with central differences in the form C3 is used. 'up-scheme' First-order upstream scheme. The upstream scheme is guarantees only a stable solution in combination with timestep_scheme = 'euler' . Note, this scheme is very diffusive, and hence, not well-suited for turbulence-resolving simulations.
ngsrb	I	2	Number of Gauss-Seidel iterations to be carried out on each grid level of the multigrid Poisson solver. In case of using the multigrid method for solving the Poisson equation for perturbation pressure (see psolver), this parameter defines the number of Gauss-Seidel iterations to be carried out on each grid level. High numbers give better convergence. The default value of 2 reduces the divergence of the preliminary velocity field by about 1-2 orders of magnitude, which is sufficient in most cases. The value of ngsrb has a significant effect on the CPU requirement of the run.
nsor	I	20	Number of iterations to be used with the SOR-scheme. This parameter is only effective if the SOR-scheme is selected as pressure solver (psolver = 'sor' ). The number of iterations necessary for a sufficient convergence of the scheme depends on the grid point numbers and is to be determined by appropriate test runs (the default value will not at all be sufficient for larger grid point numbers). The number of iterations used for the first call of the SOR-scheme (t = 0) is determined via the parameter nsor_ini.
nsor_ini	I	100	Initial number of iterations with the SOR algorithm. This parameter is only effective if the SOR algorithm was selected as the pressure solver scheme (psolver = 'sor' ) and specifies the number of initial iterations of the SOR scheme (at t = 0). The number of subsequent iterations at the following time steps is determined with the parameter nsor. Usually, nsor < nsor_ini, since in each case subsequent calls to psolver use the solution of the previous call as the initial value. Suitable test runs should determine whether sufficient convergence of the solution is obtained with the default value and if necessary the value of nsor_ini should be changed.
omega_sor	R	1.8	Convergence factor to be used with the SOR-scheme. If the SOR-scheme is selected (psolver = 'sor' ), this parameter determines the value of the convergence factor, where 1.0 <= omega_sor < 2.0. The optimum value of omega_sor depends on the number of grid points along the different directions in space. For non-equidistant grids, it can only be determined by appropriate test runs.
psolver	C*10	'poisfft'	Scheme to be used to solve the Poisson equation for the perturbation pressure. The user can choose between the following schemes: 'poisfft' Direct method using FFT along x and y, solution of a tridiagonal matrix along z, and backward FFT (see Siano, institute reports, volume 54). The FFT routines to be used can be determined via the initialization parameter fft_method. This solver is specially optimized for 1d domain decompositions. Vectorization is optimized for domain decompositions along x only. 'multigrid' Multigrid scheme (see Diplomarbeit J. Uhlenbrock?, in German only). v- and w-cycles (see cycle_mg) are implemented. The convergence of the iterative scheme can be steered by the number of v-/w-cycles to be carried out for each call of the scheme (mg_cycles) and by the number of Gauss-Seidel iterations (see ngsrb) to be carried out on each grid level. Instead, the requested accuracy can be given via residual_limit. This is the default! The smaller this limit is, the more cycles have to be carried out in this case and the number of cycles may vary from time step to time step. If mg_cycles is set to its optimal value, the computing time of the multigrid scheme amounts approximately to that of the direct solver 'poisfft', as long as the number of grid points in the three directions of space corresponds to a power-of-two (2ⁿ) where n >= 5 must hold. With large n, the multigrid scheme can even be faster than the direct solver (although its accuracy is several orders of magnitude worse, but this does not affect the accuracy of the simulation). Nevertheless, the user should always carry out some test runs in order to find out the optimum value for mg_cycles, because the CPU time of a run very critically depends on this parameter. This scheme requires that the number of grid points of the subdomains (or of the total domain, if only one PE is used) along each of the directions can, at least, be divided once by 2 without rest. With parallel runs, starting from a certain grid level the data of the subdomains are possibly gathered on PE0 in order to allow for a further coarsening of the grid. The grid level for gathering can be manually set by mg_switch_to_pe0_level. 'multigrid' is highly optimized for better performance. Data along the `k` index (vertical direction) is sorted from alternate even and odd indices into two blocks of completely even and odd indices respectively, which allows vectorization on INTEL processors of loops in the red/black scheme. Additionally, topography flags are completely ignored (i.e. not used) in case of masking_method switched off. On fine grid levels only even or odd data are send for the lateral ghost point exchange. Speedup of the multigrid solver for medium sized cases (10241024192 grid points) can be about 40% compared to 'multigrid_noopt'. In contrast to 'multigrid_noopt', masking is always used, i.e. the solver runs through the topography similar to the FFT. 'multigrid_noopt' Similar as 'multigrid', but less optimized. However, in contrast to 'multigrid', 'multigrid_noopt' allows masking_method=.FALSE., i.e. setting of Neumann boundary conditions for the perturbation pressure at all wall boundaries. Please note, in combination with masking_method, the 'multigrid_noopt' solver can lead to a blow-up of wind velocity in case of narrow street canyons or complex shapes resolved by only a few grid points. Please see further remarks. Please note: In former revisions (<1931), the naming convention for the multigrid solvers was different, 'multigrid_noopt' (now) was 'multigrid' (<1931), and 'multigrid' (now) was 'multigrid_fast' (<1931). 'sor' Successive over-relaxation method (SOR). The convergence of this iterative scheme is steered with the parameters omega_sor, nsor_ini and nsor. Compared to the direct method and the multigrid method, this scheme needs substantially more computing time. It should only be used for test runs, e.g. to compare results with the other pressure solver methods. In case of using a multistep Runge-Kutta time step scheme (see timestep_scheme), the Poisson equation is by default solved after each of the substeps. In order to speed-up performance, the Poisson equation may be solved only for the last substep (see call_psolver_at_all_substeps).
pt_damping_factor	R	0.0	Factor for damping the potential temperature. In case of non-cyclic lateral boundary conditions (see bc_lr or bc_ns), a damping is applied to the potential temperature if a non-zero value is assigned to pt_damping_factor. If switched on, the temperature is forced towards the value of its basic state (defined by the initial profile of the temperature). The intensity of damping is controlled by the value pt_damping_factor. The damping starts weakly at a distance from the inflow boundary defined by pt_damping_width and rises according to a sin²-function to its maximum value at the inflow. This method effectively damps gravity waves at the inflow boundary in case of non-cyclic lateral boundary conditions (see bc_lr or bc_ns). If the damping factor is too low, gravity waves can develop within the damping domain and if the damping factor is too high, gravity waves can develop in front of the damping domain. Detailed information about the damping can be found in the documentation of the non-cyclic lateral boundary conditions.
pt_damping_width	R	0.0	Width of the damping domain of the potential temperature (in m). In case of non-cyclic lateral boundary conditions (see bc_lr or bc_ns), this parameter determines the range where damping of the potential temperature is applied. The damping domain starts at the inflow boundary and ranges to the value of pt_damping_width. The intensity of the damping is applied by pt_damping_factor. Detailed information about the damping can be found in the documentation of the non-cyclic lateral boundary conditions.
random_generator	C*20	'random- parallel'	Random number generator to be used for creating uniformly distributed random numbers. It is used if random perturbations are to be imposed on the velocity field or on the surface heat flux field (see create_disturbances and random_heatflux). By default, the "parallel" random number generator is used. By setting ( random_generator = 'numerical-recipes' ) PALM provides exactly the same order of random numbers on all different machines and should be used in particular for comparison runs. By setting ( random_generator = 'random-parallel' ) a fully parallelized random number generator can be chosen. Like the default, this generator creates random numbers in a reproducible order. The parallel random number generator also provides ensemble run capability, which can be steered by specifying the parameter ensemble_member_nr Besides, a system-specific generator is available ( random_generator = 'system-specific' ) which should particularly be used for runs on vector parallel computers (NEC), because the default generator cannot be vectorized and therefore significantly drops down the code performance on these machines. Note: Results from two otherwise identical model runs will not compare one-to-one if they have used different random number generators, or if they are different members of an ensemble of runs (see parameter ensemble_member_nr).
rayleigh_damping_factor	R	0.0	Factor for Rayleigh damping. A so-called Rayleigh damping is applied to all prognostic variables if a non-zero value is assigned to rayleigh_damping_factor. If switched on, horizontal velocities, temperature, humidity/scalar (if switched on) and salinity (in case of ocean) are forced towards the value of their respective basic states (defined by the initial profiles of the geostrophic wind, temperature, etc.). In case of large-scale subsidence (see subs_vertical_gradient) the basic state of temperature and humidity is adjusted with respect to the subsidence. Scalar quantities can be excluded from the damping (see scalar_rayleigh_damping). The intensity of damping is controlled by the value the rayleigh_damping_factor is assigned to. The damping starts weakly at a height defined by rayleigh_damping_height and rises according to a sin²-function to its maximum value at the top (ocean: bottom) boundary. This method effectively damps gravity waves, caused by boundary layer convection, which may spread out vertically in the inversion layer and which are reflected at the top (ocean: bottom) boundary. The Rayleigh damping factor must hold the condition 0.0 <= rayleigh_damping_factor <= 1.0. Large values (close to 1.0) can cause numerical instabilities.
rayleigh_damping_height	R	2/3zu(nzt) (ocean: 2/3zu(nzb))	Height above (ocean: below) which the Rayleigh damping starts (in m). With Rayleigh damping switched on (see rayleigh_damping_factor), this parameter determines the range where damping is applied. By default, Rayleigh damping will be applied in the upper (ocean: lower) third of the model domain.
residual_limit	R	1.0E-4	Largest residual permitted for the multigrid scheme (in s^-2m^-3). This is a parameter to steer the accuracy of the multigrid scheme (see psolver). The divergence of the 3D velocity field will be reduced iteratively as long as the calculated residual is greater than residual_limit. After a maximum number of 1000 iterative cycles, PALM aborts with a corresponding error message. The reciprocal value of this parameter can be interpreted as a factor by the divergence of the provisional velocity field is approximately reduced after the multigrid scheme has been applied (thus, the default value causes a reduction of the divergence by approx. 6 orders of magnitude).
scalar_advec	C*10	'ws-scheme'	Advection scheme to be used for the scalar quantities. The user can choose between the following schemes: 'ws-scheme' The 5th order upwind scheme of Wicker and Skamarock (2002, Mon. Wea. Rev, 130, 2088-2097) is used. The dispersion error is much smaller than the dispersion error of 'pw-scheme' . The 5th order scheme implies a small numerical dissipation that stabilizes the solution. To assure a stable numerical solution the time integration has to be carried out with timestep_scheme = 'runge-kutta-3' . This scheme is based on a formulation of the advection term in flux form, which requires a vanishing divergence of the flow field, else a stable numerical solution is not given. So call_psolver_at_all_substeps = .T. has to be used. Note: Due to the larger stencil of this scheme vertical grid stretching should be handled with care. The computation of turbulent fluxes takes place inside the advection routines to get a statistical evaluation consistent to the numerical solution. 'pw-scheme' The scheme of Piacsek and Williams (1970, J. Comp. Phys., 6, 392-405) with central differences in the form C3 is used. 'bc-scheme' The Bott scheme modified by Chlond (1994, Mon. Wea. Rev., 122, 111-125). This is a conservative monotonous scheme with very small numerical diffusion and therefore very good conservation of scalar flow features. The scheme, however, is computationally very expensive both because it is expensive itself and because it does (so far) not allow specific code optimizations (e.g. cache optimization). Choice of this scheme forces the Euler time step scheme to be used for the scalar quantities. For output of horizontally averaged profiles of the resolved / total heat flux, data_output_pr = 'wptBC' / 'wptBC' should be used, instead of the standard profiles ( 'wpt' and 'wpt' ) because these are too inaccurate with this scheme. However, for subdomain analysis (see statistic_regions) exactly the reverse holds: here 'wptBC' and 'wptBC' show very large errors and should not be used. This scheme is not allowed for non-cyclic lateral boundary conditions (see bc_lr and bc_ns) and requires that loop_optimization = 'vector' is set. 'up-scheme' First-order upstream scheme. The upstream scheme is guarantees only a stable solution in combination with timestep_scheme = 'euler' . Note, this scheme is very diffusive, and hence, not well-suited for turbulence-resolving simulations. Remark: Independent on the choice of 'scalar_advec' and timestep_scheme, a different advection scheme can be chosen for the subgrid-scale TKE using parameter use_upstream_for_tke.
scalar_rayleigh_damping	L	.T.	Application of Rayleigh damping to scalars. With Rayleigh damping switched on (see rayleigh_damping_factor), this parameter determines if the damping is applied also to scalars (temperature, humidity/scalar, salinity) or to the horizontal velocity components only.
timestep_scheme	C*20	'runge kutta-3'	Time step scheme to be used for the integration of the prognostic variables. The user can choose between the following schemes: 'runge-kutta-3' Third order Runge-Kutta scheme. This scheme requires the use of momentum_advec = scalar_advec = 'ws-scheme' or 'pw-scheme'. For further information see here. 'runge-kutta-2' Second order Runge-Kutta scheme. For special features see timestep_scheme = 'runge-kutta-3'. 'euler' First order Euler scheme. A differing time step scheme can be chosen for the subgrid-scale TKE using parameter use_upstream_for_tke.
transpose_compute_overlap	L	.F.	Parameter to switch on parallel execution of fft and transpositions (with `MPI_ALLTOALL`). If the fft-Poisson-solver is used (see psolver), transpose_compute_overlap = .T. causes the fft to be executed in parallel to the transposition (done by `MPI_ALLTOALL`). For larger grids, this method may speed up the fft-solver significantly.
use_upstream_for_tke	L	.F.	Parameter to choose the advection/time step scheme to be used for the subgrid-scale TKE. By default, the advection scheme and the time step scheme to be used for the subgrid-scale TKE are set by the initialization parameters scalar_advec and timestep_scheme, respectively. use_upstream_for_tke = .T. forces the Euler-scheme and the upstream-scheme to be used as time step scheme and advection scheme, respectively. By these methods, strong artificial near-surface vertical gradients of the subgrid-scale TKE, as they will be caused by non-diffusive advection schemes, are avoided. use_upstream_for_tke = .T. is required when subgrid-scale velocities are used for advection of particles (see particle package parameter use_sgs_for_particles) and scalar_advec /= 'ws-scheme'.

Physics:

Parameter Name

FORTRAN
Type

Default
Value

Explanation

omega

7.29212E-5

Angular velocity of the rotating system (in rad/s).

The angular velocity of the earth is set by default. The values of the Coriolis parameters are calculated as:

f = 2.0 * omega * sin(phi)
f* = 2.0 * omega * cos(phi)

phi

55.0

Geographical latitude (in degrees).

The value of this parameter determines the value of the Coriolis parameters f and f*, provided that the angular velocity (see omega) is non-zero.

prandtl_number

1.0

Ratio of the eddy diffusivities for momentum and heat (K_m/K_h).

For runs with constant eddy diffusivity (see km_constant), this parameter can be used to assign the Prandtl number (ratio K_m / K_h).

Boundary conditions:

Parameter Name	FORTRAN Type	Default Value	Explanation
bc_e_b	C*20	'neumann'	Bottom boundary condition of the TKE. bc_e_b must be set to 'neumann' i.e. e(k=0)=e(k=1) (Neumann boundary condition), where e(k=1) is calculated via the prognostic TKE equation. At the top boundary a Neumann boundary condition is generally used: (e(nz+1) = e(nz)).
bc_lr	C*20	'cyclic' ('nested' for nest domains except if nesting_mode='vertical')	Boundary condition along x (for all quantities). By default, a cyclic boundary condition is used along x. bc_lr may also be assigned the values 'dirichlet/radiation' (inflow from left, outflow to the right) or 'radiation/dirichlet' (inflow from right, outflow to the left). This requires the multigrid method to be used for solving the Poisson equation for perturbation pressure (see psolver) and it also requires cyclic boundary conditions along y (see bc_ns). In case of these non-cyclic lateral boundaries, a Dirichlet condition is used at the inflow for all quantities (initial vertical profiles - see initializing_actions - are fixed during the run) except e, to which a Neumann (zero gradient) condition is applied. At the outflow, a radiation condition is used for all velocity components and the calculation method of the required phase velocity is controlled by the parameter use_cmax. For scalars, a Neumann condition is used. For the perturbation pressure, Neumann conditions are assumed both at the inflow and at the outflow. In order to maintain a turbulent state of the flow, it may be necessary to continuously impose perturbations on the horizontal velocity field in the vicinity of the inflow throughout the whole run. This can be switched on using create_disturbances. The horizontal range to which these perturbations are applied is controlled by the parameters inflow_disturbance_begin and inflow_disturbance_end. The vertical range and the perturbation amplitude are given by disturbance_level_b, disturbance_level_t, and disturbance_amplitude. The time interval at which perturbations are to be imposed is set by dt_disturb. Note that these inflow perturbances are added in addition to the standard perturbances that are activated with create_disturbances. The standard perturbances can be deactivated by setting the d3par-parameter disturbance_energy_limit = 0.0 . In case of non-cyclic horizontal boundaries call_psolver_at_all_substeps = .T. should be used. In case of nested run, except if nesting_mode= 'vertical' , the default value of 'bc_lr' in the nest domains is not 'cyclic' but 'nested' instead. For the root domain of a nested run the default is 'cyclic' as usually. Note: Using non-cyclic lateral boundaries requires very sensitive adjustments of the inflow (vertical profiles) and the bottom boundary conditions, e.g. a surface heating should not be applied near the inflow boundary because this may significantly disturb the inflow. Please check the model results very carefully. Detailed information can be found in the documentation of the non-cyclic lateral boundary conditions.
bc_ns	C*20	'cyclic' ('nested' for nest domains except if nesting_mode='vertical')	Boundary condition along y (for all quantities). By default, a cyclic boundary condition is used along y. bc_ns may also be assigned the values 'dirichlet/radiation' (inflow from rear ("north"), outflow to the front ("south")) or 'radiation/dirichlet' (inflow from front ("south"), outflow to the rear ("north")). This requires the multigrid method to be used for solving the Poisson equation for perturbation pressure (see psolver) and it also requires cyclic boundary conditions along x (see bc_lr). In case of these non-cyclic lateral boundaries, a Dirichlet condition is used at the inflow for all quantities (initial vertical profiles - see initializing_actions - are fixed during the run) except e, to which a Neumann (zero gradient) condition is applied. At the outflow, a radiation condition is used for all velocity components and the calculation method of the required phase velocity is controlled by the parameter use_cmax. For scalars, a Neumann (zero gradient) condition is used. For the perturbation pressure, Neumann (zero gradient) conditions are assumed both at the inflow and at the outflow. In case of nested run, except if nesting_mode= 'vertical' , the default value of 'bc_lr' in the nest domains is not 'cyclic' but 'nested' instead. For the root domain of a nested run the default is 'cyclic' as usually. For further details regarding non-cyclic lateral boundary conditions see bc_lr.
bc_p_b	C*20	'neumann'	Bottom boundary condition of the perturbation pressure. Allowed values are 'dirichlet' and 'neumann' . 'dirichlet' sets p(k=0)=0.0, 'neumann' sets p(k=0)=p(k=1). Since vertical velocity is zero at the rigid lower boundary (w(k=0) = 0.0), the consistent Neumann condition ( 'neumann' ) dp/dz = 0 should be used, which leaves the vertical component w unchanged, when the pressure solver is applied. Simultaneous use of the Neumann boundary conditions both at the bottom and at the top boundary (bc_p_t) is allowed.
bc_p_t	C*20	'dirichlet' ('neumann' for nest domains)	Top boundary condition of the perturbation pressure. Allowed values are 'dirichlet' (p(k=nz+1)= 0.0) or 'neumann' (p(k=nz+1)=p(k=nz)). Simultaneous use of Neumann boundary conditions both at the top and bottom boundary (bc_p_b) yields no consistent solution for the perturbation pressure in case that the multigrid method is used for solving the Poisson equation (see psolver), and should be avoided. Since at the bottom boundary the Neumann condition is a good choice (see bc_p_b), in that case, a Dirichlet condition should be set at the top boundary. In case of nested run, the default value of bc_p_t in the nest domains is not 'dirichlet' but 'neumann' instead. For the root domain of a nested run the default is 'dirichlet' as usually. Note: The nest-domain default boundary conditions for perturbation pressure lead to Poisson problem with all-Neumann boundary condition. This means that the solution is only determined up to a constant. In other words, the average value of the pressure remains arbitrary. This implies that the convergence rate is usually somewhat lower than when Dirichlet condition is used at least on one of the boundaries. The average perturbation pressure can be forced to a given value, say zero, but according to the tests, it does not improve the convergence rate at all. Users using the nesting system should pay attention to this and adjust the steering parameters of the multigrid solver carefully to achieve sufficient convergence without sacrificing too much computing time for the perturbation-pressure solution.
bc_pt_b	C*20	'dirichlet'	Bottom boundary condition of the potential temperature. Allowed values are 'dirichlet' (pt(k=0) = const. = pt_surface + pt_surface_initial_change (the user may change this value during the run using user-defined code) and 'neumann' (pt(k=0)=pt(k=1)). When a constant surface sensible heat flux is used (surface_heatflux), bc_pt_b = 'neumann' must be used, because otherwise the resolved scale may contribute to the surface flux so that a constant value cannot be guaranteed. In the coupled atmosphere executable, bc_pt_b is internally set and does not need to be prescribed.
bc_pt_t	C*20	'initial_gradient' ('nested' for nest domains)	Top boundary condition of the potential temperature. Allowed are the values 'dirichlet' (pt(k=nz+1) does not change during the run), 'neumann' (pt(k=nz+1)=pt(k=nz)), and 'initial_gradient' . With the 'initial_gradient' -condition the value of the temperature gradient at the top is calculated from the initial temperature profile (see pt_surface, pt_vertical_gradient) by bc_pt_t_val = (pt_init(k=nz+1) - pt_init(k=nz)) / dzu(nz+1). Using this value (assumed constant during the run) the temperature boundary values are calculated as pt(k=nz+1) = pt(k=nz) + bc_pt_t_val * dzu(nz+1) (up to k=nz the prognostic equation for the temperature is solved). When a constant sensible heat flux is used at the top boundary (top_heatflux), bc_pt_t = 'neumann' must be used, because otherwise the resolved scale may contribute to the top flux so that a constant value cannot be guaranteed. In case of nested run, the default value of bc_pt_t in the nest domains is not 'initial_gradient' but 'nested' instead. For the root domain of a nested run the default is 'initial_gradient' as usually.
bc_q_b	C*20	'dirichlet'	Bottom boundary condition of the specific humidity / total water content. Allowed values are 'dirichlet' (q(k=0) = const. = q_surface + q_surface_initial_change (the user may change this value during the run using user-defined code) and 'neumann' (q(k=0)=q(k=1)). When a constant surface latent heat flux is used (surface_waterflux), bc_q_b = 'neumann' must be used, because otherwise the resolved scale may contribute to the surface flux so that a constant value cannot be guaranteed.
bc_q_t	C*20	'neumann' ('nested' for nest domains)	Top boundary condition of the specific humidity / total water content. Allowed are the values 'dirichlet' (q(k=nz+1) does not change during the run) and 'neumann' . With the Neumann boundary condition the value of the humidity gradient at the top is calculated from the initial humidity profile (see q_surface, q_vertical_gradient) by: bc_q_t_val = ( q_init(k=nz) - q_init(k=nz-1)) / dzu(nz). Using this value (assumed constant during the run) the humidity boundary values are calculated as q(k=nz+1) =q(k=nz) + bc_q_t_val * dzu(nz+1) (up to k=nz the prognostic equation for q is solved). In case of nested run, the default value of bc_q_t in the nest domains is not 'neumann' but 'nested' instead. For the root domain of a nested run the default is 'neumann' as usually.
bc_s_b	C*20	'dirichlet'	Bottom boundary condition of the scalar concentration. Allowed values are 'dirichlet' (s(k=0) = const. = s_surface + s_surface_initial_change; the user may change this value during the run using #user-defined code) and 'neumann' (s(k=0) = s(k=1)). When a constant surface concentration flux is used (surface_scalarflux), bc_s_b = 'neumann' must be used, because otherwise the resolved scale may contribute to the surface flux so that a constant value cannot be guaranteed.
bc_s_t	C*20	'initial_gradient' ('nested' for nest domains)	Top boundary condition of the scalar concentration. Allowed are the values 'dirichlet' (s(k=nz+1) does not change during the run), 'neumann' (s(k=nz+1) = s(k=nz)), and 'initial_gradient' . With the 'initial_gradient' boundary condition the value of the scalar concentration gradient at the top is calculated from the initial scalar concentration profile (see s_surface, s_vertical_gradient) by: bc_s_t_val = (s_init(k=nz) - s_init(k=nz-1)) / dzu(nz). Using this value (assumed constant during the run) the concentration boundary values are calculated as s(k=nz+1) = s(k=nz) + bc_s_t_val * dzu(nz+1) (up to k=nz the prognostic equation for the scalar concentration is solved). When a constant scalar flux is used at the top boundary (top_scalarflux), bc_s_t = 'neumann' must be used, because otherwise the resolved scale may contribute to the top flux so that a constant value cannot be guaranteed. In case of nested run, the default value of bc_s_t in the nest domains is not 'initial_gradient' but 'nested' instead. For the root domain of a nested run the default is 'initial_gradient' as usually.
bc_sa_t	C*20	'neumann'	Top boundary condition of the salinity. This parameter only comes into effect for ocean runs (see parameter ocean). Allowed are the values 'dirichlet' (sa(k=nz+1) does not change during the run) and 'neumann' (sa(k=nz+1)=sa(k=nz)). When a constant salinity flux is used at the top boundary (top_salinityflux), bc_sa_t = 'neumann' must be used, because otherwise the resolved scale may contribute to the top flux so that a constant value cannot be guaranteed.
bc_uv_b	C*20	'dirichlet'	Bottom boundary condition of the horizontal velocity components u and v. Allowed values are 'dirichlet' and 'neumann' . bc_uv_b = 'dirichlet' yields the no-slip condition with u=v=0 at the bottom. The Neumann boundary condition yields the free-slip condition with u(k=0) = u(k=1) and v(k=0) = v(k=1). With a constant flux layer switched on (see constant_flux_layer) at the bottom boundary, the free-slip condition is not allowed (otherwise the run will be terminated).
bc_uv_t	C*20	'dirichlet' ('nested' for nest domains)	Top boundary condition of the horizontal velocity components u and v. Allowed values are 'dirichlet' , 'dirichlet_0' and 'neumann' . The Dirichlet condition yields u(k=nz+1) = ug(nz+1) and v(k=nz+1) = vg(nz+1), Neumann condition yields the free-slip condition with u(k=nz+1) = u(k=nz) and v(k=nz+1) = v(k=nz) (up to k=nz the prognostic equations for the velocities are solved). The special condition 'dirichlet_0' can be used for channel flow, it yields the no-slip condition u(k=nz+1) = ug(nz+1) = 0 and v(k=nz+1) = vg(nz+1) = 0. In the coupled ocean executable, bc_uv_t is internally set ('neumann') and does not need to be prescribed. In case of nested run the default value of bc_uv_t in the nest domains is not 'dirichlet' but 'nested' instead. For the root domain of a nested run the default is 'dirichlet' as usually.
bottom_salinityflux	R	0.0	Kinematic salinity flux near the surface (in psu m/s). This parameter only comes into effect for ocean runs (see parameter ocean). The respective salinity flux value is used as bottom (horizontally homogeneous) boundary condition for the salinity equation. This additionally requires that a Neumann condition must be used for the salinity, which is currently the only available condition.
constant_flux_layer	L	.T.	Parameter to switch on a constant flux layer at the bottom boundary. By default, a constant flux layer is switched on at the bottom boundary between z = 0 and z = 0.5 * dz (the first computational grid point above ground for u, v and the scalar quantities). In this case, at the bottom boundary, free-slip conditions for u and v (see bc_uv_b) are not allowed. Likewise, laminar simulations with constant eddy diffusivities (km_constant) are forbidden. With a constant flux layer switched off at the bottom, the pressure boundary condition bc_p_b = 'neumann+inhomo' is not allowed. If the constant flux layer is switched off and fluxes shall be prescribed at the surface (by setting surface_heatflux), it is required to set the parameter use_surface_fluxes = .T.. The roughness length is declared via the parameter roughness_length.
inflow_damping_height	R	from precursor run	Height below which the turbulence signal is used for turbulence recycling (in m). In case of a turbulent inflow (see turbulent_inflow), this parameter defines the vertical thickness of the turbulent layer up to which the turbulence extracted at the recycling plane (see recycling_width) shall be imposed to the inflow. Above this level, the turbulence signal is linearly damped to zero. The transition range within which the signal falls to zero is given by the parameter inflow_damping_width. By default, this height is set as the height of the convective boundary layer as calculated from a precursor run. Information about proper settings for getting this CBL height from a precursor run can be found here.
inflow_damping_width	R	0.1 * inflow_damping _height	Transition range within which the turbulence signal is damped to zero (in m). See inflow_damping_height for an explanation.
inflow_disturbance_begin	I	MIN(10, nx/2 or ny/2)	Lower limit of the horizontal range for which random perturbations are to be imposed on the horizontal velocity field (grid points). If non-cyclic lateral boundary conditions are used (see bc_lr or bc_ns), this parameter gives the grid point number (counted horizontally from the inflow) from which on perturbations are imposed on the horizontal velocity field. Perturbations must be switched on with parameter create_disturbances. Note that these inflow perturbances are added in addition to the standard perturbances that are activated with create_disturbances.
inflow_disturbance_end	I	MIN(100, 3/4nx or 3/4ny)	Upper limit of the horizontal range for which random perturbations are to be imposed on the horizontal velocity field (grid points). If non-cyclic lateral boundary conditions are used (see bc_lr or bc_ns), this parameter gives the grid point number (counted horizontally from the inflow) up to which perturbations are imposed on the horizontal velocity field. Perturbations must be switched on with parameter create_disturbances.
most_method	C*8	'lookup'	Parameter that defines how the Obukhov length is calculated when a constant_flux_layer is switched on. Available methods are: 'circular': A fast method that was the previous default in PALM. Here, the Obukhov length is calculated based on the values of t* (and q) calculated from the previous time step. This circular calculation leads to a time lag in the Obukhov length and is thus inaccurate. 'newton': The Obukhov length is calculated by means of the Richardson number and a Newton iteration algorithm. This method yields correct values of the Obukhov length, but it is slower than the 'circular' and 'lookup' methods. Furthermore, it cannot be vectorized. 'lookup*': This method is similar to the Newton iteration method, but the iteration is avoided by creating a lookup table of the Obukhov length against Richardson number at the beginning of the simulation. This method yields accurate values of the Obukhov length while being less computationally expensive compared to the Newton iteration method. However, it cannot be used in case of varying roughness lengths (unless the roughness lengths are locally homogeneous on each processor domain).
outflow_source_plane	R	-	Position of the vertical source plane from where instantaneous values of u, v, w, pt, q, s, and e are copied to the outflow boundary in case of turbulent_outflow=.True.. The source plane must be positioned inside the model domain.
recycling_width	R	-	Distance of the recycling plane from the inflow boundary (in m). This parameter sets the horizontal extension (along the direction of the main flow) of the so-called recycling domain which is used to generate a turbulent inflow (see description of turbulent inflow). recycling_width must be larger than the grid spacing (dx) and smaller than the length of the total domain (nx * dx).
recycling_yshift	L	.F.	Parameter to switch on a y-shift for the recycled inflow turbulence. If recycling_yshift = .T., the recycled turbulence that is mapped from the recycling plane (see recycling_width) to the inflow boundary is shifted in y-direction. This parameter reduces persistent streaks that may occur within the recycling domain. The distance of the y-shift is INT(npey / 2), which is in most cases the best distance for effectively reducing streaks in the recycling domain. Note that recycling_yshift = .T. requires turbulent_inflow = .T..
roughness_length	R	0.1	Roughness length (in m). The roughness length for scalars can be given a value different from the one for momentum (see z0h_factor). This parameter is effective only in case that a constant flux layer is switched on at the bottom boundary (see constant_flux_layer).
sa_vertical_gradient	R(10)	10 * 0.0	Salinity gradient(s) of the initial salinity profile (in psu / 100 m). This parameter only comes into effect for ocean runs (see parameter ocean). This salinity gradient holds starting from the height level defined by sa_vertical_gradient_level (precisely: for all uv levels k where zu(k) < sa_vertical_gradient_level, sa_init(k) is set: sa_init(k) = sa_init(k+1) - dzu(k+1) * sa_vertical_gradient) down to the bottom boundary or down to the next height level defined by sa_vertical_gradient_level. A total of 10 different gradients for 11 height intervals (10 intervals if sa_vertical_gradient_level(1) = 0.0) can be assigned. The surface salinity at k=nzt is assigned via sa_surface. Example: sa_vertical_gradient = 1.0, 0.5, sa_vertical_gradient_level = -500.0, -1000.0, That defines the salinity to be constant down to z = -500.0 m with a salinity given by sa_surface. For -500.0 m < z <= -1000.0 m the salinity gradient is 1.0 psu / 100 m and for z < -1000.0 m down to the bottom boundary it is 0.5 psu / 100 m (it is assumed that the assigned height levels correspond with uv levels).
sa_vertical_gradient_level	R(10)	10 * 0.0	Height level from which on the salinity gradient defined by sa_vertical_gradient is effective (in m). This parameter only comes into effect for ocean runs (see parameter ocean). The height levels have to be assigned in descending order. The default values result in a constant salinity profile regardless of the values of sa_vertical_gradient (unless the bottom boundary of the model is lower than -100000.0 m). For the piecewise construction of salinity profiles see sa_vertical_gradient.
surface_heatflux	R	no prescribed heatflux	Kinematic sensible heat flux at the bottom surface (in K m/s). If a value is assigned to this parameter, the internal two-dimensional surface heat flux field shf is initialized with the value of surface_heatflux as the bottom (horizontally homogeneous) boundary condition for the temperature equation. This additionally requires that a Neumann condition must be used for the potential temperature (see bc_pt_b), because otherwise the resolved scale may contribute to the surface flux so that a constant value cannot be guaranteed. Also, changes of the surface temperature (see pt_surface_initial_change) are not allowed. The parameter random_heatflux can be used to impose random perturbations on the (homogeneous) surface heat flux field shf. Attention: Setting of surface_heatflux requires setting of use_surface_fluxes = .T., if the constant flux layer is switched off (constant_flux_layer = .F.). In case of a non-flat topography, the internal two-dimensional surface heat flux field shf is initialized with the value of surface_heatflux at the bottom surface and wall_heatflux(0) at the topography top face. The parameter random_heatflux can be used to impose random perturbations on this combined surface heat flux field shf. If no surface heat flux is assigned, shf is calculated at each time step by u_* `` theta_ (of course only with constant_flux_layer switched on). Here, u_* and theta_* are calculated from Monin-Obukhov similarity theory assuming logarithmic wind and temperature profiles between k=0 and k=1. In this case, a Dirichlet condition (see bc_pt_b) must be used as bottom boundary condition for the potential temperature. Non-zero values must not be given for surface_heatflux in case of simulations with pure neutral stratification (see parameter neutral). See also top_heatflux.
surface_scalarflux	R	no prescribed scalarflux	Scalar flux at the surface (in kg/(m² s)). If a non-zero value is assigned to this parameter, the respective scalar flux value is used as bottom (horizontally homogeneous) boundary condition for the scalar concentration equation. This additionally requires that a Neumann condition must be used for the scalar concentration (see bc_s_b), because otherwise the resolved scale may contribute to the surface flux so that a constant value cannot be guaranteed. Also, changes of the surface scalar concentration (see s_surface_initial_change) are not allowed. If no surface scalar flux is assigned (surface_scalarflux = 0.0), it is calculated at each time step by u_* `` s_ (of course only with constant_flux_layer switched on). Here, s_* is calculated from Monin-Obukhov similarity theory assuming a logarithmic scalar concentration profile between k=0 and k=1. In this case, a Dirichlet condition (see bc_s_b) must be used as bottom boundary condition for the scalar concentration.
surface_waterflux	R	no prescribed waterflux	Kinematic water flux near the surface (in kg/kg m/s). If a non-zero value is assigned to this parameter, the respective water flux value is used as bottom (horizontally homogeneous) boundary condition for the humidity equation. This additionally requires that a Neumann condition must be used for the specific humidity / total water content (see bc_q_b), because otherwise the resolved scale may contribute to the surface flux so that a constant value cannot be guaranteed. Also, changes of the surface humidity (see q_surface_initial_change) are not allowed. If no surface water flux is assigned (surface_waterflux = 0.0), it is calculated at each time step by u_* `` q_ (of course only with a constant flux layer switched on). Here, q_* is calculated from Monin-Obukhov similarity theory assuming a logarithmic temperature profile between k=0 and k=1. In this case, a Dirichlet condition (see bc_q_b) must be used as the bottom boundary condition for the humidity.
top_heatflux	R	no prescribed heatflux	Kinematic sensible heat flux at the top boundary (in K m/s). If a value is assigned to this parameter, the internal two-dimensional surface heat flux field `tswst` is initialized with the value of top_heatflux as the top (horizontally homogeneous) boundary condition for the temperature equation. This additionally requires that a Neumann condition must be used for the potential temperature (see bc_pt_t), because otherwise the resolved scale may contribute to the top flux so that a constant flux value cannot be guaranteed. Note: The application of a top heat flux additionally requires the setting of initial parameter use_top_fluxes = .T.. No constant flux layer is available at the top boundary so far. Non-zero values must not be given for top_heatflux in case of simulations with pure neutral stratification (see parameter neutral). See also surface_heatflux.
top_momentumflux_u	R	no prescribed momentumflux	Momentum flux along x at the top boundary (in m²/s²). If a value is assigned to this parameter, the internal two-dimensional u-momentum flux field `uswst` is initialized with the value of top_momentumflux_u as the top (horizontally homogeneous) boundary condition for the u-momentum equation. Notes: The application of a top momentum flux additionally requires the setting of initial parameter use_top_fluxes = .T.. Setting of top_momentumflux_u requires setting of top_momentumflux_v also. A Neumann condition should be used for the u velocity component (see bc_uv_t), because otherwise the resolved scale may contribute to the top flux so that a constant flux value cannot be guaranteed. No constant flux layer is available at the top boundary so far. The coupled ocean parameter file PARIN_O should include dummy REAL value assignments to both top_momentumflux_u and top_momentumflux_v (e.g. top_momentumflux_u = 0.0, top_momentumflux_v = 0.0) to enable the momentum flux coupling.
top_momentumflux_v	R	no prescribed momentumflux	Momentum flux along y at the top boundary (in m²/s²). If a value is assigned to this parameter, the internal two-dimensional v-momentum flux field `vswst` is initialized with the value of top_momentumflux_v as the top (horizontally homogeneous) boundary condition for the v-momentum equation. Notes: The application of a top momentum flux additionally requires the setting of initial parameter use_top_fluxes = .T.. Setting of top_momentumflux_v requires setting of top_momentumflux_u also. A Neumann condition should be used for the v velocity component (see bc_uv_t), because otherwise the resolved scale may contribute to the top flux so that a constant flux value cannot be guaranteed. No constant flux layer is available at the top boundary so far. The coupled ocean parameter file PARIN_O should include dummy REAL value assignments to both top_momentumflux_u and top_momentumflux_v (e.g. top_momentumflux_u = 0.0, top_momentumflux_v = 0.0) to enable the momentum flux coupling.
top_salinityflux	R	no prescribed salinityflux	Kinematic salinity flux at the top boundary, i.e. the sea surface (in psu m/s). This parameter only comes into effect for ocean runs (see parameter ocean). If a value is assigned to this parameter, the internal two-dimensional surface heat flux field `saswst` is initialized with the value of top_salinityflux as top (horizontally homogeneous) boundary condition for the salinity equation. This additionally requires that a Neumann condition must be used for the salinity (see bc_sa_t), because otherwise the resolved scale may contribute to the top flux so that a constant flux value cannot be guaranteed. Note: The application of a salinity flux at the model top additionally requires the setting of initial parameter use_top_fluxes = .T.. See also bottom_salinityflux.
top_scalarflux	R	no prescribed scalarflux	Scalar flux at the top boundary (in kg/kg m/s). If a value is assigned to this parameter, the internal two-dimensional surface scalar flux field `sswst` is initialized with the value of top_scalarflux as the top (horizontally homogeneous) boundary condition for the scalar equation. This additionally requires that a Neumann condition must be used for the scalar (see bc_s_t), because otherwise the resolved scale may contribute to the top flux so that a constant flux value cannot be guaranteed. Note: The application of a top scalar flux additionally requires the setting of initial parameter use_top_fluxes = .T.. No constant flux layer is available at the top boundary so far.
turbulent_inflow	L	.F.	Generates a turbulent inflow at side boundaries using a turbulence recycling method. Turbulent inflow is realized using the turbulence recycling method from Lund et al. (1998, J. Comp. Phys., 140, 233-258) modified by Kataoka and Mizuno (2002, Wind and Structures, 5, 379-392). A turbulent inflow requires Dirichlet conditions at the respective inflow boundary. So far, a turbulent inflow is realized from the left (west) side only, i.e. bc_lr = 'dirichlet/radiation' is required! The initial (quasi-stationary) turbulence field must be generated by a precursor run and used by setting initializing_actions = 'cyclic_fill'. The distance of the recycling plane from the inflow boundary can be set with parameter recycling_width. The height above ground above which the turbulence signal is not used for recycling and the width of the layer within the magnitude of the turbulence signal is damped from 100% to 0% can be set with parameters inflow_damping_height and inflow_damping_width. The detailed setup for a turbulent inflow is described in here.
turbulent_outflow	L	.F.	When set true, a turbulent outflow condition is used at the outflow boundary. This outflow condition works similar to the turbulent recycling method, but instantaneous values are copied from a vertical source plane (see outflow_sourec_plane) from inside the domain to the outflow boundary. This prevents numerical errors which can occur if negative velocity values appear at the outflow boundary while using the radiation boundary condition. For using this outflow method bc_lr = 'dirichlet/radiation' is required. This method can only be used for an outflow boundary at the right model boundary, so far. The vertical source plane from where to copy the values of u, v, w, pt, q, s, and e should be placed not too close to the outflow boundary.
use_cmax	L	.T.	Parameter to choose the calculation method of the phase velocity at the outflow boundary in case of non-cyclic lateral boundary conditions. In case of non-cyclic lateral boundary conditions (see bc_lr and bc_ns), radiation boundary conditions are used for the velocity components at the outflow boundary. If use_cmax = .T., the phase velocity is set to the maximum value that ensures numerical stability (CFL-condition). With this method, the radiation boundary conditions are simplified, as phase velocity must not be calculated. Setting use_cmax = .F., the phase velocity is calculated after every time step, using the approach of Orlanski (1976). Additionally, local phase velocities are averaged along the outflow boundary in each height level. Detailed information can be found in the documentation of the non-cyclic lateral boundary conditions.
use_surface_fluxes	L	.F.	Parameter to steer the treatment of the subgrid-scale vertical fluxes within the diffusion terms at k=1 (bottom boundary). By default, the near-surface subgrid-scale fluxes are parameterized (like in the remaining model domain) using the gradient approach. If use_surface_fluxes = .T., the user-assigned surface fluxes are used instead (see surface_heatflux, surface_waterflux and surface_scalarflux) or the surface fluxes are calculated via Monin-Obukhov similarity theory (depends on the bottom boundary conditions, see bc_pt_b, bc_q_b and bc_s_b). use_surface_fluxes is automatically set .T., if a constant flux layer is used (see constant_flux_layer). The user may prescribe the surface fluxes at the bottom boundary without using a constant flux layer by setting use_surface_fluxes = .T. and constant_flux_layer = .F.. If, in this case, the momentum flux (u_*²) should also be prescribed, the user must assign an appropriate value within the user-defined code.
use_top_fluxes	L	.F.	Parameter to steer the treatment of the subgrid-scale vertical fluxes within the diffusion terms at k=nz (top boundary). By default, the fluxes at nz are calculated using the gradient approach. If use_top_fluxes = .T., the user-assigned top fluxes are used instead (see top_heatflux, top_momentumflux_u, top_momentumflux_v, top_salinityflux). Currently, no value for the latent heatflux can be assigned. In case of use_top_fluxes = .T., the latent heat flux at the top will be automatically set to zero.
wall_adjustment	L	.T.	Parameter to restrict the mixing length in the vicinity of the bottom boundary (and near vertical walls of a non-flat topography). With wall_adjustment = .T., the mixing length is limited to a maximum of 1.8 * z. This condition typically affects only the first grid points above the bottom boundary. In case of a non-flat topography, the respective horizontal distance from vertical walls is used.
z0h_factor	R	1.0	Factor for calculating the roughness length for scalars. This parameter can be used to define a value for the roughness length for scalars (potential temperature, humidity/scalar) which differs from the one for momentum. The roughness length for scalars z0h is calculated as: z0h = z0h_factor * roughness_length. This parameter is effective only in case that a constant flux layer is switched on at the bottom boundary (see constant_flux_layer).
zeta_max	R	20.0	Upper limit of the stability parameter `[zeta = z_mo/L`, with `z_mo` being the height of the constant flux layer, and `L` being the Obukhov length. With a constant flux layer switched on (see constant_flux_layer), the Obukhov length (ol) is calculated for `z=z_mo (k=1)` in the 3d-model (in the 1d-model for all heights) for each horizontal grid point. Its particular values determine the values of the friction velocity (1d- and 3d-model) and the values of the eddy diffusivity (1d-model). With small wind velocities at the top of the constant flux layer or small vertical wind shears in the 1d-model, the stability parameter zeta = z_mo/ol can take up unrealistic values. They are limited by an upper (zeta_max) and lower limit (see zeta_min). The condition zeta_max > zeta_min must be met.
zeta_min	R	-20.0	Lower limit of the stability parameter `[zeta = z_mo/L`, with `z_mo` being the height of the constant flux layer, and `L` being the Obukhov length. For further explanations see zeta_max. The condition zeta_max > zeta_min must be met.

Initialization:

Parameter Name	FORTRAN Type	Default Value	Explanation
damp_level_1d	R	zu(nzt+1)	Height where the damping layer begins in the 1d-model (in m). This parameter is used to switch on a damping layer for the 1d-model, which is generally needed for the damping of inertia oscillations. Damping is done by gradually increasing the value of the eddy diffusivities about 10% per vertical grid level (starting with the value at the height given by damp_level_1d, or possibly from the next grid point above), i.e. K_m(k+1) = 1.1 * K_m(k). The values of K_m are limited to 10 m²/s at maximum. This parameter only comes into effect if the 1d-model is switched on for the initialization of the 3d-model using initializing_actions = 'set_1d-model_profiles'.
dissipation_1d	C*20	'detering'	Calculation method for the energy dissipation term in the TKE equation of the 1d-model. By default (since r1691) dissipation_1d = 'detering' forces the dissipation to be calculated as diss = 0.064 * e``1.5 / l. When setting dissipation_1d** = 'as_in_3d_model' (default before r1691), the dissipation is calculated as in the 3d-model using diss = (0.19 + 0.74 * l / l_grid) * e`**`1.5 / l.
dt	R	variable	Time step for the 3d-model (in s). By default, (i.e. if a Runge-Kutta scheme is used, see timestep_scheme) the value of the time step is calculating after each time step (following the time step criteria) and used for the next step. If the user assigns dt a value, then the time step is fixed to this value throughout the whole run (whether it fulfills the time step criteria or not). However, changes are allowed for restart runs, because dt can also be used as a run parameter. In case that the calculated time step meets the condition dt < 0.00001 * dt_max (with dt_max = 20.0) the simulation will be aborted. Such situations usually arise in case of any numerical problem / instability which causes a non-realistic increase of the wind speed. A small time step due to a large mean horizontal wind speed may be enlarged by using a coordinate transformation (see galilei_transformation), in order to spare CPU time.
dt_pr_1d	R	9999999.9	Temporal interval of vertical profile output of the 1d-model (in s). Data are written in ASCII format to file LIST_PROFIL_1D. This parameter is only in effect if the 1d-model has been switched on for the initialization of the 3d-model with initializing_actions = 'set_1d-model_profiles'.
dt_run_control_1d	R	60.0	Temporal interval of runtime control output of the 1d-model (in s). Data are written in ASCII format to file RUN_CONTROL. This parameter is only in effect if the 1d-model is switched on for the initialization of the 3d-model with initializing_actions = 'set_1d-model_profiles'.
end_time_1d	R	864000.0	Time to be simulated for the 1d-model (in s). The default value corresponds to a simulated time of 10 days. Usually, after such a period the inertia oscillations have completely decayed and the solution of the 1d-model can be regarded as stationary (see damp_level_1d). This parameter is only in effect if the 1d-model is switched on for the initialization of the 3d-model with initializing_actions = 'set_1d-model_profiles'.
ensemble_member_nr	I	0	By setting the initialization parameter ensemble_member_nr to an integer between 1 and 2000, palm will produce statistically independent members of a simulation. This parameter can only be used, if random_generator = 'random-parallel' is set.
initializing_actions	C*100		Initialization actions to be carried out. This parameter does not have a default value and ,therefore, must be assigned with each model run. For restart runs initializing_actions = 'read_restart_data' must be set. For the initial run of a job chain the following values are allowed: 'set_constant_profiles' A horizontal wind profile consisting of linear sections (see ug_surface, ug_vertical_gradient, ug_vertical_gradient_level and vg_surface, vg_vertical_gradient, vg_vertical_gradient_level, respectively) as well as a vertical temperature (humidity) profile consisting of linear sections (see pt_surface, pt_vertical_gradient, q_surface and q_vertical_gradient) are assumed as initial profiles. The subgrid-scale TKE is set to 0 but K_m and K_h are set to very small values because otherwise no TKE would be generated. Instead of using the geostrophic wind for constructing the initial u,v-profiles, these profiles can also be directly set using parameters u_profile, v_profile, and uv_heights, e.g. if observed profiles shall be used as initial values. In runs with non-cyclic horizontal boundary conditions these profiles are also used as fixed mean inflow profiles. 'set_1d-model_profiles' The arrays of the 3d-model are initialized with the (stationary) solution of the 1d-model. These are the variables e, K_h`,` K_m`,` u, v and with a constant flux layer switched on ol, us, usws, vsws. The temperature (humidity) profile consisting of linear sections is set as for 'set_constant_profiles' and assumed as constant in time within the 1d-model. For steering of the 1d-model a set of parameters with suffix "_1d" (e.g. end_time_1d, damp_level_1d) is available. 'by_user' The initialization of the arrays of the 3d-model is under complete control of the user and has to be done in routine `user_init_3d_model` of the user-interface. 'initialize_vortex' The initial velocity field of the 3d-model corresponds to a Rankine-vortex with a vertical axis. This setting may be used to test advection schemes. Free-slip boundary conditions for u and v (see bc_uv_b, bc_uv_t) are necessary. In order not to distort the vortex, an initial horizontal wind profile constant with height is necessary (to be set by initializing_actions = 'set_constant_profiles`'`) and some other conditions have to be met (neutral stratification, diffusion must be switched off, see km_constant). The center of the vortex is located at jc = (nx+1)/2. It extends from k = 0 to k = nz+1. Its radius is 8 * dx and the exponentially decaying part ranges to 32 * dx (see `init_rankine.f90`). 'initialize_ptanom' A 2d-Gauss-like shape disturbance (x,y) is added to the initial temperature field with radius 10.0 * dx and center at jc = (nx+1)/2. This may be used for tests of scalar advection schemes (see scalar_advec). Such tests require a horizontal wind profile constant with height and diffusion switched off (see 'initialize_vortex' ). Additionally, the buoyancy term must be switched off in the equation of motion for w (this requires the user to comment out the call of buoyancy in the source code of `prognostic_equations.f90`). 'cyclic_fill' Here, 3d-data from a precursor run are read by the initial (main) run. The precursor run is allowed to have a smaller domain along x and y compared with the main run. Also, different numbers of processors can be used for these two runs. Limitations are that the precursor run must use cyclic horizontal boundary conditions and that the number of vertical grid points, nz, must be same for the precursor run and the main run. If the total domain of the main run is larger than that of the precursor run, the domain is filled by cyclic repetition of the (cyclic) precursor data. This initialization method is required if a turbulent inflow is used (see turbulent_inflow). 3d-data must be made available to the run by activating an appropriate file connection statement for local file BININ. The usage of a turbulent inflow is explained here. Note that in case of reference_state= 'initial_profile', the main run uses the initial profile of the precursor run. Values may be combined, e.g. initializing_actions = 'set_constant_profiles initialize_vortex' , but the values of 'set_constant_profiles' , 'set_1d-model_profiles' , and 'by_user' must not be given at the same time.
mixing_length_1d	C*20	'blackadar'	Mixing length used in the 1d-model. By default, mixing_length_1d = 'blackadar', the so-called Blackadar mixing length is used (l = kappa * z / ( 1 + kappa * z / lambda ) with the limiting value lambda = 2.7E-4 * u_g / f). By setting mixing_length_1d = 'as_in_3d_model', the mixing length is calculated as in the 3d-model (i.e. it depends on the grid spacing).
pt_surface	R	300.0	Surface potential temperature (in K). This parameter assigns the value of the potential temperature pt at the surface (k=0). Starting from this value, the initial vertical temperature profile is constructed with pt_vertical_gradient and pt_vertical_gradient_level. This profile is also used for the 1d-model as a stationary profile. Attention: In case of ocean runs (see ocean), this parameter gives the temperature value at the sea surface, which is at k=nzt. The profile is then constructed from the surface down to the bottom of the model.
pt_surface_initial_change	R	0.0	Change in surface temperature to be made at the beginning of the 3d run (in K). If pt_surface_initial_change is set to a non-zero value, the near surface sensible heat flux is not allowed to be given simultaneously (see surface_heatflux).
pt_vertical_gradient	R(10)	10*0.0	Temperature gradient(s) of the initial temperature profile (in K / 100 m). This temperature gradient holds starting from the height level defined by pt_vertical_gradient_level (precisely: for all uv levels k where zu(k) > pt_vertical_gradient_level, pt_init(k) is set: pt_init(k) = pt_init(k-1) + dzu(k) * pt_vertical_gradient) up to the top boundary or up to the next height level defined by pt_vertical_gradient_level. Below the first prescribed height level, the temperature is automatically set constant with height. A total of 10 different gradients for 11 height intervals (10 intervals if pt_vertical_gradient_level(1) = 0.0) can be assigned. The surface temperature is assigned via pt_surface. Example: pt_vertical_gradient = 1.0, 0.5, pt_vertical_gradient_level = 500.0, 1000.0, That defines the temperature profile to be neutrally stratified up to z = 500.0 m with a temperature given by pt_surface. For 500.0 m < z <= 1000.0 m the temperature gradient is 1.0 K / 100 m and for z > 1000.0 m up to the top boundary it is 0.5 K / 100 m (it is assumed that the assigned height levels correspond with uv levels). Attention: In case of ocean runs (see ocean), the profile is constructed like described above, but starting from the sea surface (k=nzt) down to the bottom boundary of the model. Height levels have then to be given as negative values, e.g. pt_vertical_gradient_level = -500.0, -1000.0.
pt_vertical_gradient_level	R(10)	10*0.0	Height level above which the temperature gradient defined by pt_vertical_gradient is effective (in m). The height levels have to be assigned in ascending order. The default values result in a neutral stratification regardless of the values of pt_vertical_gradient (unless the top boundary of the model is higher than 100000.0 m). For the piecewise construction of temperature profiles see pt_vertical_gradient. Attention: In case of ocean runs (see ocean), the (negative) height levels have to be assigned in descending order.
q_surface	R	0.0	Surface specific humidity / total water content (kg/kg). This parameter assigns the value of the specific humidity q at the surface (k=0). Starting from this value, the initial humidity profile is constructed with q_vertical_gradient and q_vertical_gradient_level. This profile is also used for the 1d-model as a stationary profile.
q_surface_initial_change	R	0.0	Change in surface specific humidity / total water content to be made at the beginning of the 3d run (kg/kg). If q_surface_initial_change is set to a non-zero value the near surface latent heat flux (water flux) is not allowed to be given simultaneously (see surface_waterflux).
q_vertical_gradient	R(10)	10 * 0.0	Humidity gradient(s) of the initial humidity profile (in 1/100 m). This humidity gradient holds starting from the height level defined by q_vertical_gradient_level (precisely: for all uv levels k, where zu(k) > q_vertical_gradient_level, q_init(k) is set: q_init(k) = q_init(k-1) + dzu(k) * q_vertical_gradient) up to the top boundary or up to the next height level defined by q_vertical_gradient_level. A total of 10 different gradients for 11 height intervals (10 intervals if q_vertical_gradient_level(1) = 0.0) can be asigned. The surface humidity is assigned via q_surface. Example: q_vertical_gradient = 0.001, 0.0005, q_vertical_gradient_level = 500.0, 1000.0, That defines the humidity to be constant with height up to z = 500.0 m with a value given by q_surface. For 500.0 m < z <= 1000.0 m the humidity gradient is 0.001 / 100 m and for z > 1000.0 m up to the top boundary it is 0.0005 / 100 m (it is assumed that the assigned height levels correspond with uv levels).
q_vertical_gradient_level	R(10)	10 * 0.0	Height level from which on the humidity gradient defined by q_vertical_gradient is effective (in m). The height levels are to be assigned in ascending order. The default values result in a humidity constant with height regardless of the values of q_vertical_gradient (unless the top boundary of the model is higher than 100000.0 m). For the piecewise construction of humidity profiles see q_vertical_gradient.
sa_surface	R	35.0	Surface salinity (in psu). This parameter only comes into effect for ocean runs (see parameter ocean). This parameter assigns the value of the salinity sa at the sea surface (k=nzt). Starting from this value, the initial vertical salinity profile is constructed from the surface down to the bottom of the model (k=0) by using sa_vertical_gradient and sa_vertical_gradient_level.
spinup_pt_amplitude	R	0.0	Representative amplitude of the diurnal near-surface temperature variation during the spinup phase (see spinup_time). Note that this amplitude does not match the true temperature amplitude during spinup. The true amplitude depends also on the incoming shortwave radiation and thus depends on the day of the year and the geographic location.
spinup_pt_mean	R	value of pt_surface	Mean near-surface air temperature during the spinup phase (see spinup_time). If no value is provided, the mean will be inferred from the setting of pt_surface.
spinup_time	R	0.0	Parameter for steering of the spinup time. Depending on the model components switched on, these can run in a spinup phase without an interactive atmosphere. Currently, this mechanism is implemented for the land surface and the urban surface model. In the spinup phase, these models predict the skin and soil/wall temperatures. For using the spinup mechanism it is required to have a radiation model activated. Forcing is achieved by radiation and optionally a varying near-surface air temperature (steered via spinup_pt_mean, spinup_pt_amplitude, and the incoming solar radiation. After completion of the spinup, the atmospheric code is switched on and runs coupled to the surface models. Note that the near-surface temperatures are reset before coupling to their initial values prescribed by the user. The spinup mechanism can be steered via the additional parameters dt_spinup and data_output_during_spinup.
surface_pressure	R	1013.25	Atmospheric pressure at the surface (in hPa). Starting from this surface value, the vertical pressure profile is calculated once at the beginning of the run assuming a neutrally stratified atmosphere. This is needed for converting between the liquid water potential temperature and the potential temperature (see cloud_physics).
s_surface	R	0.0	Surface value of the passive scalar (in kg/m³). This parameter assigns the value of the passive scalar s at the surface (k=0). Starting from this value, the initial vertical scalar concentration profile is constructed with s_vertical_gradient and s_vertical_gradient_level.
s_surface_initial_change	R	0.0	Change in surface scalar concentration to be made at the beginning of the 3d run (in kg/m³). If s_surface_initial_change is set to a non-zero value, the near surface scalar flux is not allowed to be given simultaneously (see surface_scalarflux).
s_vertical_gradient	R(10)	10 * 0.0	Scalar concentration gradient(s) of the initial scalar concentration profile (in kg/m³ / 100 m). The scalar gradient holds starting from the height level defined by s_vertical_gradient_level (precisely: for all uv levels k, where zu(k) > s_vertical_gradient_level, s_init(k) is set: s_init(k) = s_init(k-1) + dzu(k) * s_vertical_gradient) up to the top boundary or up to the next height level defined by s_vertical_gradient_level. A total of 10 different gradients for 11 height intervals (10 intervals if s_vertical_gradient_level(1) = 0.0) can be assigned. The surface scalar value is assigned via s_surface. Example: s_vertical_gradient = 0.1, 0.05, s_vertical_gradient_level = 500.0, 1000.0, That defines the scalar concentration to be constant with height up to z = 500.0 m with a value given by. For 500.0 m < z <= 1000.0 m the scalar gradient is 0.1 kg/m³ / 100 m and for z > 1000.0 m up to the top boundary it is 0.05 kg/m³ / 100 m (it is assumed that the assigned height levels correspond with uv levels).
s_vertical_gradient_level	R(10)	10 * 0.0	Height level from which on the scalar gradient defined by s_vertical_gradient is effective (in m). The height levels are to be assigned in ascending order. The default values result in a scalar concentration constant with height regardless of the values of s_vertical_gradient (unless the top boundary of the model is higher than 100000.0 m). For the piecewise construction of scalar concentration profiles see s_vertical_gradient.
u_profile	R(100)	100 * 9999999.9	Values of u-velocity component to be used as initial profile (in m/s). The corresponding height levels have to be provided by parameter uv_heights. The first velocity value always has to be assigned to the surface and must be zero, i.e. `u_profile(1)` = 0.0. Velocity values for the model grid levels are calculated from the given values by linear interpolation. If the uppermost value is given for a height smaller than the domain height, this value will be used for all grid points above this level. In runs with non-cyclic horizontal boundary conditions this profile will be used as fixed mean inflow profile.
ug_surface	R	0.0	u-component of the geostrophic wind at the surface (in m/s). This parameter assigns the value of the u-component of the geostrophic wind (ug) at the surface (k=0). Starting from this value, the initial vertical profile of the u-component of the geostrophic wind is constructed with ug_vertical_gradient and ug_vertical_gradient_level. The profile constructed in that way is used for creating the initial vertical velocity profile of the 3d-model. Either it is applied, as it has been specified by the user (initializing_actions = 'set_constant_profiles' ) or it is used for calculating a stationary boundary layer wind profile (initializing_actions = 'set_1d-model_profiles' ). If ug is constant with height (i.e. ug(k) = ug_surface) and has a large value, it is recommended to use a Galilei-transformation of the coordinate system, if possible (see galilei_transformation), in order to obtain larger time steps. Attention: In case of ocean runs (see ocean), this parameter gives the u-component of the geostrophic velocity value (i.e. the pressure gradient) at the sea surface, which is at k=nzt. The profile is then constructed from the surface down to the bottom of the model.
ug_vertical_gradient	R(10)	10 * 0.0	Gradient(s) of the initial profile of the u-component of the geostrophic wind (in 1/100s). The gradient holds starting from the height level defined by ug_vertical_gradient_level (precisely: for all uv levels k where zu(k) > ug_vertical_gradient_level, ug(k) is set: ug(k) = ug(k-1) + dzu(k) * ug_vertical_gradient) up to the top boundary or up to the next height level defined by ug_vertical_gradient_level. A total of 10 different gradients for 11 height intervals (10 intervals if ug_vertical_gradient_level(1) = 0.0) can be assigned. The surface geostrophic wind is assigned by ug_surface. Attention: In case of ocean runs (see ocean), the profile is constructed like described above, but starting from the sea surface (k=nzt) down to the bottom boundary of the model. Height levels have then to be given as negative values, e.g. ug_vertical_gradient_level = -500.0, -1000.0.
ug_vertical_gradient_level	R(10)	10 * 0.0	Height level from which on the gradient defined by ug_vertical_gradient is effective (in m). The height levels have to be assigned in ascending order. For the piecewise construction of a profile of the u-component of the geostrophic wind component (ug) see ug_vertical_gradient. Attention: In case of ocean runs (see ocean), the (negative) height levels have to be assigned in descending order.
uv_heights	R(100)	100 * 9999999.9	Height levels in ascending order (in m), for which prescribed u,v-velocities are given (see u_profile, v_profile. The first height level must always be zero, i.e. uv_heights(1) = 0.0.
v_profile	R(100)	100 * 9999999.9	Values of v-velocity component to be used as initial profile (in m/s). The corresponding height levels have to be provided by parameter uv_heights. The first velocity value always has to be given for the surface and must be zero, i.e. `v_profile(1)` = 0.0. Velocity values for the model grid levels are calculated from the given values by linear interpolation. If the uppermost value is given for a height smaller than the domain height, this value will be used for all grid points above this level. In runs with non-cyclic horizontal boundary conditions this profile will be used as fixed mean inflow profile.
vg_surface	R	0.0	v-component of the geostrophic wind at the surface (in m/s). This parameter assigns the value of the v-component of the geostrophic wind (vg) at the surface (k=0). Starting from this value, the initial vertical profile of the v-component of the geostrophic wind is constructed with vg_vertical_gradient and vg_vertical_gradient_level. The profile constructed in that way is used for creating the initial vertical velocity profile of the 3d-model. Either it is applied, as it has been specified by the user (initializing_actions = 'set_constant_profiles' ) or it is used for calculating a stationary boundary layer wind profile (initializing_actions = 'set_1d-model_profiles' ). If vg is constant with height (i.e. vg(k)=vg_surface) and has a large value, it is recommended to use a Galilei-transformation of the coordinate system, if possible (see galilei_transformation), in order to obtain larger time steps. Attention: In case of ocean runs (see ocean), this parameter gives the v-component of the geostrophic velocity value (i.e. the pressure gradient) at the sea surface, which is at k=nzt. The profile is then constructed from the surface down to the bottom of the model.
vg_vertical_gradient	R(10)	10 * 0.0	Gradient(s) of the initial profile of the v-component of the geostrophic wind (in 1/100s). The gradient holds starting from the height level defined by vg_vertical_gradient_level (precisely: for all uv levels k where zu(k) > vg_vertical_gradient_level, vg(k) is set: vg(k) = vg(k-1) + dzu(k) * vg_vertical_gradient) up to the top boundary or up to the next height level defined by vg_vertical_gradient_level. A total of 10 different gradients for 11 height intervals (10 intervals if vg_vertical_gradient_level(1) = 0.0) can be assigned. The surface geostrophic wind is assigned by vg_surface. Attention: In case of ocean runs (see ocean), the profile is constructed like described above, but starting from the sea surface (k=nzt) down to the bottom boundary of the model. Height levels have then to be given as negative values, e.g. vg_vertical_gradient_level = -500.0, -1000.0.
vg_vertical_gradient_level	R(10)	10 * 0.0	Height level from which on the gradient defined by vg_vertical_gradient is effective (in m). The height levels have to be assigned in ascending order. For the piecewise construction of a profile of the v-component of the geostrophic wind component (vg) see vg_vertical_gradient. Attention: In case of ocean runs (see ocean), the (negative) height levels have to be assigned in descending order.

Topography:

Parameter Name	FORTRAN Type	Default Value	Explanation
building_height	R	50.0	Height of a single building in m. building_height must be less than the height of the model domain. This parameter requires the use of topography = 'single_building'.
building_length_x	R	50.0	Width of a single building in m. Currently, building_length_x must be at least 3 * dx and no more than ( nx - 1 ) * dx - building_wall_left. This parameter requires the use of topography = 'single_building'.
building_length_y	R	50.0	Depth of a single building in m. Currently, building_length_y must be at least 3 * dy and no more than ( ny - 1 ) * dy - building_wall_south. This parameter requires the use of topography = 'single_building'.
building_wall_left	R	building centered in x-direction	x-coordinate of the left building wall (distance between the left building wall and the left border of the model domain) in m. Currently, building_wall_left must be at least 1 * dx and less than ( nx - 1 ) * dx - building_length_x. This parameter requires the use of topography = 'single_building'. The default value building_wall_left = ( ( nx + 1 ) * dx - building_length_x ) / 2 centers the building in x-direction. Due to the staggered grid the building will be displaced by -0.5 dx in x-direction and -0.5 dy in y-direction.
building_wall_south	R	building centered in y-direction	y-coordinate of the south building wall (distance between the south building wall and the south border of the model domain) in m. Currently, building_wall_south must be at least 1 * dy and less than ( ny - 1 ) * dy - building_length_y. This parameter requires the use of topography = 'single_building'. The default value building_wall_south = ( ( ny + 1 ) * dy - building_length_y ) / 2 centers the building in y-direction. Due to the staggered grid the building will be displaced by -0.5 dx in x-direction and -0.5 dy in y-direction.
canyon_height	R	50.0	Street canyon height in m. canyon_height must be less than the height of the model domain. This parameter requires topography = 'single_street_canyon'.
canyon_width_x	R	9999999.9	Street canyon width in x-direction in m. Currently, canyon_width_x must be at least 3 * dx and no more than ( nx - 1 ) * dx - canyon_wall_left. This parameter requires topography = 'single_street_canyon'. A non-default value implies a canyon orientation in y-direction.
canyon_width_y	R	9999999.9	Street canyon width in y-direction in m. Currently, canyon_width_y must be at least 3 * dy and no more than ( ny - 1 ) * dy - canyon_wall_south. This parameter requires topography = 'single_street_canyon'. A non-default value implies a canyon orientation in x-direction.
canyon_wall_left	R	canyon centered in x-direction	x-coordinate of the left canyon wall (distance between the left canyon wall and the left border of the model domain) in m. Currently, canyon_wall_left must be at least 1 * dx and less than ( nx - 1 ) * dx - canyon_width_x. This parameter requires topography = 'single_street_canyon'. The default value canyon_wall_left = ( ( nx + 1 ) * dx - canyon_width_x ) / 2 centers the canyon in x-direction.
canyon_wall_south	R	canyon centered in y-direction	y-coordinate of the south canyon wall (distance between the south canyon wall and the south border of the model domain) in m. Currently, canyon_wall_south must be at least 1 * dy and less than ( ny - 1 ) * dy - canyon_width_y. This parameter requires topography = 'single_street_canyon'. The default value canyon_wall_south = ( ( ny + 1 ) * dy - canyon_width_y ) / 2 centers the canyon in y-direction.
topography	C*40	'flat'	Topography mode. The user can choose between the following modes: 'flat' Flat surface. 'single_building' Flow around a single rectangular building mounted on a flat surface. The building size and location can be specified by the parameters building_height, building_length_x, building_length_y, building_wall_left and building_wall_south. 'single_street_canyon' Flow over a single, quasi-2D street canyon of infinite length oriented either in x- or in y-direction. The canyon size, orientation, and location can be specified by the parameters canyon_height plus either canyon_width_x and canyon_wall_left or canyon_width_y and canyon_wall_south. 'read_from_file' Flow around arbitrary topography. This mode requires the input file TOPOGRAPHY_DATA. This file contains the arbitrary topography height information in m. These data must exactly match the horizontal grid. 'tunnel' Flow within a tunnel of finite or infinite length oriented either in x- or in y-direction. The height of the tunnel outer top wall can be specified by tunnel_height. The tunnel length and width can be specified via tunnel_length and either tunnel_width_x or tunnel_width_y. Furthermore, the depth of tunnel walls can be specified by tunnel_wall_depth. Note, tunnels are always centered in the model domain along x- and y-direction. Alternatively, the user may add code to the user interface subroutine user_init_grid to allow further topography modes. These require to explicitly set the topography_grid_convention to either 'cell_edge' or 'cell_center' . Non-flat topography modes may assign a kinematic sensible wall_heatflux and a kinematic wall_humidityflux (requires humidity = .T.) or a wall_scalarflux (requires passive_scalar = .T.) at the five topography faces. All non-flat topography modes require the use of psolver /= 'sor' , alpha_surface = 0.0, galilei_transformation = .F., cloud_droplets = .F. (has not been tested), and constant_flux_layer = .T.. Note: In case there are holes in the topography that are resolved by only one grid point, the topography array in filtered so that such holes are filled up to the minimum topography height of the directly adjoining grid points in the x- and the y-direction. This is necessary, because for such chimney-like features resolved by one grid point, the continuity equation is not fulfilled on a discrete grid, as the only degree of freedom for the pressure solver is the vertical. Such holes are suspected to lead to unrealistic velocity blow-ups, hence, they are filled up. Note that an inclined model domain requires the use of topography = 'flat' and a nonzero alpha_surface.
topography_grid_convention	C*11	default depends on value of topography; see text for details	Convention for defining the topography grid. Possible values are 'cell_edge' The distance between cell edges defines the extent of topography. This setting is normally for generic topographies, i.e. topographies that are constructed using length parameters. For example, topography = 'single_building' is constructed using building_length_x and building_length_y. The advantage of this setting is that the actual size of generic topography is independent of the grid size, provided that the length parameters are an integer multiple of the grid lengths dx and dy. This is convenient for resolution parameter studies. 'cell_center' The number of topography cells defines the extent of topography. This setting is normally for rastered real topographies derived from digital elevation models. For example, topography = 'read_from_file' is constructed using the input file TOPOGRAPHY_DATA. The advantage of this setting is that the rastered topography cells of the input file are directly mapped to topography grid boxes in PALM. The example files `example_topo_file` and `example_building` in trunk/EXAMPLES/ illustrate the difference between both approaches. Both examples simulate a single building and yield the same results. The former uses a rastered topography input file with 'cell_center' convention, the latter applies a generic topography with 'cell_edge' convention. The default value is 'cell_edge' if topography = 'single_building' or 'single_street_canyon', 'cell_center' if topography = 'read_from_file', none (' ' ) otherwise, leading to an abort if topography_grid_convention is not set. This means that For PALM simulations using a user-defined topography, the topography_grid_convention must be explicitly set to either 'cell_edge' or 'cell_center'. For PALM simulations using a standard topography ( 'single_building', 'single_street_canyon' or 'read_from_file' ), it is possible but not required to set the topography_grid_convention because appropriate default values apply.
tunnel_height	R	0.2 * nz	Height of tunnel top (outer wall).
tunnel_length	R	9999999.9	Length of the tunnel. tunnel_length can be smaller (open tunnel) or larger (infinite tunnel) than the model-domain extents along the tunnel axis.
tunnel_width_x	R	9999999.9	Width of the tunnel along x-direction with respect to the tunnel outer walls. A non-default value indicates a tunnel orientation along y. The tunnel width must be at least larger than 2 * dx + 2 * tunnel_wall_depth.
tunnel_width_y	R	9999999.9	Width of the tunnel along x-direction with respect to the tunnel outer walls. A non-default value indicates a tunnel orientation along x. The tunnel width must be at least larger than 2 * dy + 2 * tunnel_wall_depth.
tunnel_wall_depth	R	max( dx, dy, dz )	Depth of the tunnel walls.
wall_heatflux	R(5)	6 * 0.0	Prescribed kinematic sensible heat flux in K m/s at the five topography faces: wall_heatflux(0) top face wall_heatflux(1) left face wall_heatflux(2) right face wall_heatflux(3) south face wall_heatflux(4) north face wall_heatflux(5) bottom face This parameter applies only in case of a non-flat topography. Prescribing wall_heatflux additionally requires setting of surface_heatflux. Furthermore, please note that wall_heatflux(0) only describes the kinematic flux at non-zero height. At zero-height (surface) the kinematic flux is given by surface_heatflux instead. The parameter random_heatflux can be used to impose random perturbations on the internal two-dimensional surface heat flux field shf that is composed of surface_heatflux at the bottom surface and wall_heatflux(0) at the topography top face.
wall_humidityflux	R(5)	5 * 0.0	Prescribed kinematic humidity flux in m/s at the five topography faces: wall_humidityflux(0) top face wall_humidityflux(1) left face wall_humidityflux(2) right face wall_humidityflux(3) south face wall_humidityflux(4) north face wall_humidityflux(5) bottom face This parameter applies only in case of a non-flat topography and humidity = .T.. Prescribing wall_humidityflux additionally requires setting of surface_waterflux. Furthermore, please note that wall_humidityflux(0) only describes the kinematic flux at non-zero height. At zero-height (surface) the kinematic flux is given by surface_waterflux instead.
wall_scalarflux	R(5)	5 * 0.0	Prescribed scalar flux in kg/(m² s) at the five topography faces: wall_scalarflux(0) top face wall_scalarflux(1) left face wall_scalarflux(2) right face wall_scalarflux(3) south face wall_scalarflux(4) north face wall_scalarflux(5) bottom face This parameter applies only in case of a non-flat topography and passive_scalar = .T.. Prescribing wall_scalarflux additionally requires setting of surface_scalarflux. Furthermore, please note that wall_scalarflux(0) only describes the kinematic flux at non-zero height. At zero-height (surface) the kinematic flux is given by surface_scalarflux instead.

Cloud physics:

Parameter Name	FORTRAN Type	Default Value	Explanation
call_microphysics_at_all_substeps	L	.F.	Parameter to control how often 2-moment cloud microphysics (cloud_scheme = 'seifert_beheng') are computed during a model time step. Using the default, cloud microphysics are computed once before the time step. Using call_microphysics_at_all_substeps = .T., cloud microphysics are computed before every substep of the applied time step scheme, which is, however, not necessary to gain acceptable results. Note that advection and diffusion of rainwater content (qr) and rain drop concentration (nr) are not affected by this parameter (these processes are computed as any other scalar).
c_sedimentation	R	2.0	Courant number for sedimentation process. A Courant number that is too big inhibits microphysical interactions of the sedimented quantity. There is no need to use the limiter (limiter_sedimentation) if c_sedimentation <= 1.0. This parameter only comes into effect if the microphysical cloud scheme according to Seifert and Beheng (2006) is used (cloud_scheme = 'seifert_beheng').
cloud_water_sedimentation	L	.F.	Parameter to consider sedimentation of cloud water according to Ackermann et al. (2009, MWR). This parameter only comes into effect if the microphysical cloud scheme according to Seifert and Beheng (2006) (cloud_scheme = 'seifert_beheng') or by Kessler (1969) (cloud_scheme = 'kessler') is used.
limiter_sedimentation	L	.T.	Slope limiter in sedimentation process according to Stevens and Seifert (2008). This parameter only comes into effect if the microphysical cloud scheme according to Seifert and Beheng (2006) is used (cloud_scheme = 'seifert_beheng'). If c_sedimentation <= 1.0 there is no need to use the limiter.
nc_const	R	70.0E6	Fixed cloud droplet number density (in 1/m³). The default value is applicable for marine conditions. This parameter only comes into effect if the microphysical cloud scheme according to Seifert and Beheng (2006) is used (cloud_scheme = 'seifert_beheng').
collision_turbulence	L	.F.	Turbulence effects on the collision process, namely the autoconversion and accretion according to Seifert, Nuijens and Stevens (2010). This parameter only comes into effect if the microphysical cloud scheme according to Seifert and Beheng (2006) is used (cloud_scheme = 'seifert_beheng').
ventilation_effect	L	.T.	Parameter to consider the ventilation effect on evaporation of raindrops according to Seifert (2008). This parameter only comes into effect if the microphysical cloud scheme according to Seifert and Beheng (2006) is used (cloud_scheme = 'seifert_beheng').

Others:

Parameter Name

FORTRAN
Type

Default
Value

Explanation

alpha_surface

0.0

Inclination of the model domain with respect to the horizontal (in degrees).

By setting alpha_surface unequal to zero the model domain can be inclined in x-direction with respect to the horizontal. In this way flows over inclined surfaces (e.g. drainage flows, gravity flows) can be simulated. In case of alpha_surface /= 0 the buoyancy term appears both in the equation of motion of the u-component and of the w-component.

An inclination is only possible in case of cyclic horizontal boundary conditions along x AND y (see bc_lr and bc_ns) and topography = 'flat'.

In the case of alpha_surface /= 0.0 the simultaneous use of humidity = .TRUE. is not allowed.

Runs with inclined surface still require additional user-defined code as well as modifications to the default code. Please ask the PALM developer group.

netcdf_precision

C*20 (10)

single precision for all output quantities

Defines the accuracy of the netCDF output.

By default, all netCDF output data have single precision (4 byte) accuracy. Double precision (8 byte) can be choosen alternatively.
Accuracy for the different output data (cross sections, 3d-volume data, spectra, etc.) can be set independently.
'<out>_NF90_REAL4' (single precision) or '<out>_NF90_REAL8' (double precision) are the two principally allowed values for netcdf_precision, where the string '<out>' can be chosen out of the following list:

'xy'	horizontal cross section
'xz'	vertical (xz) cross section
'yz'	vertical (yz) cross section
'2d'	all cross sections
'3d'	volume data
'pr'	vertical profiles
'ts'	time series, particle time series
'sp'	spectra
'prt'	particles
'all'	all output quantities

Example:
If all cross section data and the particle data shall be output in double precision and all other quantities in single precision, then netcdf_precision = '2d_NF90_REAL8' , 'prt_NF90_REAL8' has to be assigned.

statistic_regions

Number of additional user-defined subdomains for which statistical analysis and corresponding output (profiles, time series) shall be made.

By default, vertical profiles and other statistical quantities are calculated as horizontal and/or volume average of the total model domain. Beyond that, these calculations can also be carried out for subdomains which can be defined using the field rmask within the user-defined software (see User-defined domains). The number of these subdomains is determined with the parameter statistic_regions. Maximum 9 additional subdomains are allowed. The parameter region can be used to assign names (identifier) to these subdomains which are then used in the headers of the output files and plots.

Data for the total domain and all defined subdomains are output to the same file(s) (DATA_1D_PR_NETCDF, DATA_1D_TS_NETCDF). In case of statistic_regions > 0, data on the file for the different domains can be distinguished by a suffix which is appended to the quantity names. Suffix 0 means data for the total domain, suffix 1 means data for subdomain 1, etc.

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