Land Surface Parameters

Since r1551 a full land surface model (LSM) is available in PALM. It consists of a four layer soil model, predicting soil temperature and moisture content, and a solver for the energy balance at the surface. Moreover, a liquid water reservoir accounts for the presence of liquid water on plants due to dew/fog. The implementation is based on the ECMWF-IFS land surface parametrization (TESSEL) and its adaption in the DALES model. More more details, see land surface model documentation.

All parts of the LSM code are modularized in module land_surface_model_mod. In this context, a new Fortran NAMELIST lsm_par was added, containing all LSM-related steering parameters. The LSM is automatically activated when a lsm_par is set in the parameter file (_p3d). The user can easily set all relevant LSM parameters by choosing between 3 different surface types (vegetation, pavement, water) and various pre-defined surface classes 17 pre-defined vegetation types, 7 pre-defined pavement types, 4 pre-defined water types, and 6 different soil types. The default setting of the LSM is a soil of medium porosity covered to 85% with short grass. It is also possible to modify the pre-defined vegetation/soil types by overwriting some of the parameters. Moreover it is possible to create user-defined vegetation and soil types from scratch.

A minimum configuration of the LSM requires setting of the parameters soil_type, and vegetation_type. Setting of initial vertical profiles of soil_temperature and soil_moisture is recommended.

Note that the use of the LSM requires using a radiation model.

NAMELIST group name: lsm_par

Parameter Name	FORTRAN Type	Default Value	Explanation
alpha_vangenuchten	R	depending on soil_type	Value of the coefficient alpha for the calculation of the hydraulic conductivity of soil in the parametrization after Van Genuchten (1980).
c_surface	R	20000.0	Heat capacity of the surface (skin layer) per unit of area (in J/m²/K).
canopy_resistance_coefficient	R	depending on vegetation_type	A coefficient (in 1/hPa) for the dependence of the canopy resistance on water vapor pressure deficit. Only relevant for high vegetation.
conserve_water_content	L	.T.	Flag parameter for the bottom boundary condition of the soil model. The user can choose between the following two options: '.T.' Closed bottom (bedrock, no drainage). Conservation of water in the soil and atmosphere is guaranteed. '.F.' Open bottom (free drainage). Water can leave the soil model and conservation of water is not guaranteed.
field_capacity	R	depending on soil_type	Soil moisture at field capacity (in m³/m³).
f_shortwave_incoming	R	depending on vegetation_type	Fraction of the net shortwave radiation that is transmitted directly to the top soil layer. The remaining fraction of the shortwave radiation is absorbed by the surface (skin layer). This parameter has not been fully implemented yet and is fixed to 0.
hydraulic_conductivity	R	depending on soil_type	Hydraulic conductivity of the soil at saturation (in m/s).
lambda_surface_stable	R	depending on vegetation_type	Heat conductivity (between atmosphere and soil) (in W/m²/K) in case of stable stratification.
lambda_surface_unstable	R	depending on vegetation_type	Heat conductivity (between atmosphere and soil) (in W/m²/K) in case of unstable stratification.
leaf_area_index	R	depending on vegetation_type	Leaf area index of the canopy (in m²/m²).
l_vangenuchten	R	depending on soil_type	Value of the coefficient l for the calculation of the hydraulic conductivity of soil in the parametrization after Van Genuchten (1980).
min_canopy_resistance	R	depending on vegetation_type	Minimum canopy (i.e., stomatal) resistance (in s/m).
min_soil_resistance	R	50.0	Minimum soil resistance (in s/m).
pavement_depth	R	depending on pavement_type	Depth of the paved surface (m).
pavement_heat_capacity	R	depending on pavement_type	Heat capacity of the pavement.
pavement_heat_conduct	R	depending on pavement_type	Heat capacity of the pavement.
pavement_type	I	1	Pavement type classification according to the following list. 0 user defined All pavement parameters must be explicitly set by the user. 1 asphalt 2 concrete 3 asphalt/concrete mix 4 brick pavers 5 cobblestone pavers 6 sett pavers 7 gravel pavers pavement_type pavement_depth z0_pavement z0h_pavement pavement_heat_conduct pavement_heat_capacity 1 0.05 1.0E-4 1.0E-5 1.00 1.94E6 2 0.05 1.0E-4 1.0E-5 1.00 1.94E6 3 0.05 1.0E-4 1.0E-5 1.00 1.94E6 4 0.05 1.0E-4 1.0E-5 1.00 1.94E6 5 0.05 1.0E-4 1.0E-5 1.00 1.94E6 6 0.05 1.0E-4 1.0E-5 1.00 1.94E6 7 0.05 1.0E-4 1.0E-5 1.00 1.94E6
residual_moisture	R	depending on soil_type	Residual soil moisture content (in m³/m³).
saturation_moisture	R	depending on soil_type	Soil moisture at saturation (in m³/m³).
wilting_point	R	depending on soil_type	Soil moisture at permanent wilting point (in m³/m³).
n_vangenuchten	R	depending on soil_type	Value of the coefficient n for the calculation of the hydraulic conductivity of soil in the parametrization after Van Genuchten (1980).
root_fraction	R(4)	depending on vegetation_type	Root distribution over the four soil layers (with index k). It must hold that
skip_time_do_lsm	R	0.0	Time after which the land surface model is switched on. This parameter can be used to allow the LES model to develop turbulence before it is affected by the land surface.
soil_moisture	R(4)	4*0.0	Soil moisture distribution over the four soil layers (given by zs). Soil moisture is defined at the center of the soil volumes (see LSM grid) and is only predicted when humidity = .T.. Default (dry): soil_moisture = 0.0, 0.0, 0.0, 0.0 Note that the soil moisture is internally set to a minimum value according to wilting_point at model start.
soil_temperature	R(5)	see Description	Soil temperature distribution over the four soil layers in K. Default: soil_temperature = 290.0, 287.0, 285.0, 283.0, 283.0 The first four values represent the temperature of the soil layers (defined at the center of the layers of depth zs, see LSM grid. The last (fifth) value represents the deep soil temperature, which is fixed (boundary condition).
soil_type	I	3	Soil type to be used in the soil model. The user can choose from 6 soil types according to the ECMWF-IFS classification (parametrization after Van Genuchten (1980): soil_type Description Notes 0 user defined All soil-related parameters must be explicitly set by the user. 1 coarse 2 medium 3 medium-fine 4 fine 5 very fine 6 organic The following parameters will then be automatically set: alpha_vangenuchten (alpha_vg), l_vangenuchten (l_vg), n_vangenuchten (n_vg), hydraulic_conductivity (gamma_w_sat), saturation_moisture (m_sat), field_capacity (m_fc), wilting_point (m_wilt), residual_moisture (m_res). soil_type alpha_vg l_vg n_vg gamma_w_sat (m/s) m_sat (m³/m³) m_fc (m³/m³) m_wilt (m³/m³) m_res (m³/m³) 1 3.83 1.150 1.38 6.94E-6 0.403 0.244 0.059 0.025 2 3.14 -2.342 1.28 1.16E-6 0.439 0.347 0.151 0.010 3 0.83 -0.588 1.25 0.26E-6 0.430 0.383 0.133 0.010 4 3.67 -1.977 1.10 2.87E-6 0.520 0.448 0.279 0.010 5 2.65 2.500 1.10 1.74E-6 0.614 0.541 0.335 0.010 6 1.30 0.400 1.20 1.20E-6 0.766 0.663 0.267 0.010
surface_type	C	'netcdf'	Surface type classification. Allowed are 'vegetation', 'pavement', 'water', and 'netcdf'. Depdening on surface_type, the required parameters are set via setting of vegetation_type, pavement_type, or water_type. When surface_type = 'netcdf', all input data required by the LSM is expected to be provided from an NetCDF input file (NetCDF support for input files is currently under way).
vegetation_coverage	R	depending on vegetation_type	Vegetation coverage of the surface (values of 0-1). The residual fraction is considered to be bare soil.
vegetation_type	I	2	Vegetation type to be used in the land surface model. The user can choose from 19 different pre-defined vegetation classes according to the ECMWF-IFS classification: vegetation_type Description 0 user defined 1 bare soil 2 crops, mixed farming 3 short grass 4 evergreen needleleaf trees 5 deciduous needleleaf trees 5 evergreen broadleaf trees 6 deciduous broadleaf trees 7 tall grass 8 desert 9 tundra 10 irrigated crops 11 semidesert 12* ice caps and glaciers 13 bogs and marshes 14 evergreen shrubs 15 deciduous shrubs 16 mixed forest/woodland 17 interrupted forest 18 pavement/roads (* not yet implemented) The following parameters will then be automatically set: min_canopy_resistance (r_c_min), leaf_area_index (LAI), vegetation_coverage (c_veg), canopy_resistance_coefficient (gD), z0_vegetation, z0h_vegetation, lambda_surface_stable (lambda_s), lambda_surface_unstable (lambda_u), f_shortwave_incoming (f_sw_in), root_fraction. The following tables provide an overview of the parameter values. vegetation_type r_c_min (s/m) LAI (m²/m²) c_veg gD (1/hPa) z0_vegetation (m) z0h_vegetation lambda_s (W/m²/K) lambda_u (W/m²/K) f_sw_in 1 180.0 3.00 0.90 0.00 0.25 0.25E-2 10.0 10.0 0.05 2 180.0 3.00 0.90 0.00 0.25 0.25E-2 10.0 10.0 0.05 3 110.0 2.00 0.85 0.00 0.20 0.20E-2 10.0 10.0 0.05 4 500.0 5.00 0.90 0.03 2.00 2.00 20.0 15.0 0.03 5 500.0 5.00 0.90 0.03 2.00 2.00 20.0 15.0 0.03 6 175.0 5.00 0.90 0.03 2.00 2.00 20.0 15.0 0.03 7 240.0 6.00 0.99 0.13 2.00 2.00 20.0 15.0 0.03 8 100.0 2.00 0.70 0.00 0.47 0.47E-2 10.0 10.0 0.05 9 250.0 0.05 0.00 0.00 0.013 0.013E-2 15.0 15.0 0.00 10 80.0 1.00 0.50 0.00 0.034 0.034E-2 10.0 10.0 0.05 11 180.0 3.00 0.90 0.00 0.5 0.50E-2 10.0 10.0 0.05 12 150.0 0.50 0.10 0.00 0.17 0.17E-2 10.0 10.0 0.05 13* 0.0 0.00 0.00 0.00 1.3E-3 1.3E-4 58.0 58.0 0.00 14 240.0 4.00 0.60 0.00 0.83 0.83E-2 10.0 10.0 0.05 15 225.0 3.00 0.50 0.00 0.10 0.10E-2 10.0 10.0 0.05 16 225.0 1.50 0.50 0.00 0.25 0.25E-2 10.0 10.0 0.05 17 250.0 5.00 0.90 0.03 2.00 2.00E-2 20.0 15.0 0.03 18 175.0 2.50 0.90 0.03 1.10 1.10E-2 20.0 15.0 0.03 (* not yet implemented)
zs	R(4)	see description	Depths of the four soil layers (in m). Note that the model operates with negative values below the surface, data output will thus be at located at -zs. Default: zs = 0.005, 0.02, 0.04, 0.07, 0.15, 0.28, 1.00, 2.89, Schematic overview of the soil model grid:
z0_vegetation	R	depending on vegetation_type	Roughness length for momentum (in m) for vegetation surface types. The setting of z0_vegetation overwrites roughness_length, unless z0_vegetion is not set.
z0h_vegetation	R	depending on vegetation_type	Roughness length for heat (in m). The setting of z0h_vegetation overwrites z0h_factor. In this case, the roughness length for heat is calculated from z0h_factor and z0h_vegetation (or #roughness_length).
z0q_vegetation	R	depending on vegetation_type	Roughness length for moisture (in m). When z0q_vegetation is not explicitly set, it is set to the value of z0h.