| 4 | | The canopy model embedded in PALM can be used to simulate the effect of vegetation canopies on a turbulent flow.\\ Thereby, the canopy is modeled as a porous viscous medium that removes momentum from the flow (according to Shaw & Schumann, 1992; Watanabe, 2004). The presentation [/wiki/doc/tut/job/canopy#Canopymodel "Canopy model"] provides detailed information on canopy-flow theory and the functionality of the canopy model. An example on how to model the flow across a simple canopy block can be found under exercise [/wiki/doc/tut/job/canopy#Exercise9:Canopyflow "Canopy flow"].\\\\ |
| 5 | | |
| 6 | | Starting at revision 13XX (oder Release XX), all parts of the canopy-model-related PALM code are modularized in module [/browser/palm/trunk/SOURCE/plant_canopy_model.f90 plant_canopy_model_mod]. In this context, the newly created package {{{canopy_par}}} now contains all canopy-related input parameters. This means that the canopy model is now steered using the NAMELIST {{{canopy_par}}}, and no longer over the {{{inipar}}}-NAMELIST. Hence, in order to automatically enable the canopy model, NAMELIST {{{canopy_par}}} and the respective canopy parameters must be added to the parameter file ({{{_p3d}}}), subsequently to the NAMELIST {{{d3par}}}. |
| | 4 | The canopy model embedded in PALM can be used to simulate the effect of vegetation canopies on a turbulent flow.\\ Thereby, the canopy is modeled as a porous viscous medium that removes momentum from the flow (Shaw & Schumann, 1992; Watanabe, 2004). The presentation [/wiki/doc/tut/job/canopy#Canopymodel "Canopy model"] provides detailed information on canopy-flow theory and the functionality of the canopy model. An example on how to model the flow across a simple canopy block can be found under exercise [/wiki/doc/tut/job/canopy#Exercise9:Canopyflow "Canopy flow"].\\\\ |
| | 5 | |
| | 6 | Starting at '''revision 1485''', all parts of the canopy-model-related PALM code are modularized in module [/browser/palm/trunk/SOURCE/plant_canopy_model.f90 plant_canopy_model_mod]. In this context, the newly created package {{{canopy_par}}} now contains all canopy-related input parameters. This means that the canopy model is now steered using the NAMELIST {{{canopy_par}}}, and no longer with the {{{inipar}}}-NAMELIST. Hence, in order to automatically enable the canopy model, NAMELIST {{{canopy_par}}} and the respective canopy parameters must be added to the parameter file ({{{_p3d}}}), subsequently to the NAMELIST {{{d3par}}}. The setting of parameter plant_canopy = ''.T.'' is no longer required, since this is automatically done in PALM if the NAMELIST {{{canopy_par}}} exists in the parameter file. |
| 32 | | with LAI being the prescribed leaf area index [/wiki/doc/app/canpar#beta_lai \beta_lai] (LAI is the vertical integral over the LAD profile). |
| 33 | | |
| 34 | | [/wiki/doc/app/canpar#beta_lai \beta_lai] has to be set to a non-zero value in order to use the beta probability density function for the LAD-profile construction. |
| 35 | | [/wiki/doc/app/canpar#alpha_lad alpha_lad] steers together with [/wiki/doc/app/canpar#beta_lad beta_lad] the vertical distribution of leaf area within the canopy volume. [/wiki/doc/app/canpar#alpha_lad alpha_lad] can take values from XX to XX. \\\\ |
| 36 | | |
| | 32 | with the leaf area index LAI (LAI is the vertical integral over the LAD profile) being prescribed by canopy parameter [#lai_beta lai_beta].\\\\ |
| | 33 | [#lai_beta lai_beta] has to be set to a non-zero value in order to use the beta probability density function for the LAD-profile construction. |
| | 34 | '''alpha_lad''' steers together with [#beta_lad beta_lad] the vertical distribution of leaf area within the canopy volume. Values for '''alpha_lad''' must be greater than zero. Increasing [#alpha_lad alpha_lad] moves the leaf area more towards the canopy top. \\\\ |
| | 35 | '''Note:'''\\ |
| 50 | | Dimensionless coefficient required for the construction of the leaf area density (LAD) profile, using following beta probability density function (following XXcite):\\\\ |
| 51 | | {{{ |
| 52 | | #!Latex |
| 53 | | \[ f_{PDF}(\frac{z}{H},\alpha,\beta) = \frac{(\frac{z}{H})^{\alpha-1}\;(1-\frac{z}{H})^{\beta-1}}{\int_{0}^{1}\;(\frac{z}{H})^{\alpha-1}\;(1-\frac{z}{H})^{\beta-1}\;d(\frac{z}{H})}, \] |
| 54 | | }}} |
| 55 | | where ''z'' is the height above ground, ''H'' is canopy height, and alpha and beta are the coefficients to be presribed. The actual leaf area density values follow from: |
| 56 | | {{{ |
| 57 | | #!Latex |
| 58 | | \[ LAD(\frac{z}{H},\alpha,\beta) = LAI * f_{PDF}(\frac{z}{H},\alpha,\beta), \] |
| 59 | | }}} |
| 60 | | with LAI being the prescribed leaf area index [/wiki/doc/app/canpar#beta_lai \beta_lai] (LAI is the vertical integral over the LAD profile). |
| 61 | | |
| 62 | | [/wiki/doc/app/canpar#beta_lai \beta_lai] has to be set to a non-zero value in order to use the beta probability density function for the LAD-profile construction. |
| 63 | | [/wiki/doc/app/canpar#beta_lad beta_lad] steers together with [/wiki/doc/app/canpar#alpha_lad alpha_lad] the vertical distribution of leaf area within the canopy volume. [/wiki/doc/app/canpar#beta_lad beta_lad] can take values from XX to XX. \\\\ |
| 64 | | |
| 65 | | The leaf area density profile can also be constructed by prescribing vertical gradients ([/wiki/doc/app/canpar#lad_vertical_gradient_level lad_vertical_gradient_level], [/wiki/doc/app/canpar#lad_vertical_gradient lad_vertical_gradient]) of the leaf area density, starting from the prescribed surface value [/wiki/doc/app/canpar#lad_surface lad_surface]. |
| | 49 | Dimensionless coefficient required for the construction of the leaf area density (LAD) profile, using a beta probability density function (see [#alpha_lad alpha_lad] for details).\\\\ |
| | 50 | '''beta_lad''' steers together with [#alpha_lad alpha_lad] the vertical distribution of leaf area within the canopy volume. Values for '''beta_lad''' must be greater than zero. Increasing '''beta_lad''' moves the leaf area more towards the canopy floor. \\\\ |
| | 51 | '''Note:'''\\ |
| | 52 | The LAD profile can also be constructed by prescribing vertical gradients ([/wiki/doc/app/canpar#lad_vertical_gradient_level lad_vertical_gradient_level], [/wiki/doc/app/canpar#lad_vertical_gradient lad_vertical_gradient]) of the leaf area density, starting from the prescribed surface value [/wiki/doc/app/canpar#lad_surface lad_surface]. |
| 94 | | If [#plant_canopy plant_canopy] is set ''.T.'', the user can prescribe a heat flux at the top of the plant canopy. |
| 95 | | It is assumed that solar radiation penetrates the canopy and warms the foliage which, in turn, warms the air in contact with it.\\\\ |
| | 81 | The user can prescribe a heat flux at the top of the plant canopy. |
| | 82 | It is assumed that solar radiation penetrates the canopy and warms the foliage which, in turn, warms the air in contact with it. |
| | 83 | Based on '''cthf''', the heat fluxes inside the canopy down to the canopy floor ([#surface_heatflux surface_heatflux]) are determined from a decaying exponential function that is dependent on the cumulative leaf_area_index (Shaw and Schumann, 1992, BLM 61, 47-64). |
| | 84 | }}} |
| | 85 | |---------------- |
| | 86 | {{{#!td style="vertical-align:top" |
| | 87 | [=#canopy_drag_coeff '''canopy_drag_coeff'''] |
| | 88 | }}} |
| | 89 | {{{#!td style="vertical-align:top" |
| | 90 | R |
| | 91 | }}} |
| | 92 | {{{#!td style="vertical-align:top" |
| | 93 | 0.0 |
| | 94 | }}} |
| | 95 | {{{#!td |
| | 96 | Drag coefficient used in the {{{plant_canopy_model}}}.\\\\ |
| | 97 | This parameter has to be greater than zero for the simulation of a plant canopy. |
| | 98 | }}} |
| | 99 | |---------------- |
| | 100 | {{{#!td style="vertical-align:top" |
| | 101 | [=#lad_surface '''lad_surface'''] |
| | 102 | }}} |
| | 103 | {{{#!td style="vertical-align:top" |
| | 104 | R |
| | 105 | }}} |
| | 106 | {{{#!td style="vertical-align:top" |
| | 107 | 0.0 |
| | 108 | }}} |
| | 109 | {{{#!td |
| | 110 | Surface value of the leaf area density (in m^2^/m^3^).\\\\ |
| | 111 | This parameter assigns the value of the leaf area density (LAD) at the surface (k=0). Starting from this value, the LAD profile is constructed with [#lad_vertical_gradient lad_vertical_gradient] and [#lad_vertical_gradient_level lad_vertical_gradient_level].\\\\ |
| 97 | | Instead of using the value prescribed by [#surface_heatflux surface_heatflux], the near surface heat flux is determined from an exponential function that is dependent on the cumulative leaf_area_index (Shaw and Schumann (1992, Boundary Layer Meteorol., 61, 47-64)). |
| 98 | | }}} |
| 99 | | |---------------- |
| 100 | | {{{#!td style="vertical-align:top" |
| 101 | | [=#drag_coefficient '''drag_coefficient'''] |
| 102 | | }}} |
| 103 | | {{{#!td style="vertical-align:top" |
| 104 | | R |
| 105 | | }}} |
| 106 | | {{{#!td style="vertical-align:top" |
| 107 | | 0.0 |
| 108 | | }}} |
| 109 | | {{{#!td |
| 110 | | Drag coefficient used in the {{{plant_canopy_model}}}.\\\\ |
| 111 | | This parameter has to be non-zero, if the parameter [#plant_canopy plant_canopy] is set ''.T.''. |
| 112 | | }}} |
| 113 | | |---------------- |
| 114 | | {{{#!td style="vertical-align:top" |
| 115 | | [=#lad_surface '''lad_surface'''] |
| 116 | | }}} |
| 117 | | {{{#!td style="vertical-align:top" |
| 118 | | R |
| 119 | | }}} |
| 120 | | {{{#!td style="vertical-align:top" |
| 121 | | 0.0 |
| 122 | | }}} |
| 123 | | {{{#!td |
| 124 | | Surface value of the leaf area density (in m^2^/m^3^).\\\\ |
| 125 | | This parameter assigns the value of the leaf area density '''lad''' at the surface (k=0). Starting from this value, the leaf area density profile is constructed with [#lad_vertical_gradient lad_vertical_gradient] and [#lad_vertical_gradient_level lad_vertical_gradient_level]. |
| | 113 | The LAD profile can also be constructed using a beta probability density function by prescribing values for parameters [#alpha_lad alpha_lad], [#beta_lad beta_lad] and [#lai_beta lai_beta]. |
| 171 | | [=#leaf_surface_concentration '''leaf_surface_concentration'''] |
| 172 | | }}} |
| 173 | | {{{#!td style="vertical-align:top" |
| 174 | | R |
| 175 | | }}} |
| 176 | | {{{#!td style="vertical-align:top" |
| 177 | | 0.0 |
| 178 | | }}} |
| 179 | | {{{#!td |
| 180 | | Concentration of a passive scalar at the surface of a leaf (in K m/s).\\\\ |
| 181 | | This parameter is only of importance in cases in that both, [#plant_canopy plant_canopy] and [#passive_scalar passive_scalar], are set ''.T..'' The value of the concentration of a passive scalar at the surface of a leaf is required for the parametrisation of the sources and sinks of scalar concentration due to the canopy. |
| | 159 | [=#leaf_surface_conc '''leaf_surface_conc'''] |
| | 160 | }}} |
| | 161 | {{{#!td style="vertical-align:top" |
| | 162 | R |
| | 163 | }}} |
| | 164 | {{{#!td style="vertical-align:top" |
| | 165 | 0.0 |
| | 166 | }}} |
| | 167 | {{{#!td |
| | 168 | Concentration of a passive scalar at the surface of a leaf (in kg/m^3^).\\\\ |
| | 169 | This parameter is only of importance in cases where [#passive_scalar passive_scalar] = ''.T.''. The value of the concentration of a passive scalar at the surface of a leaf is required for the parametrization of the sources and sinks of scalar concentration due to the canopy. |
| 195 | | Above '''pch_index''' the arrays of leaf area density and [#drag_coeffient drag_coeffient] are automatically set to zero in case of [#plant_canopy plant_canopy] = ''.T.''. Up to '''pch_index''' a leaf area density profile can be prescribed by using the parameters [#lad_surface lad_surface], [#lad_vertical_gradient lad_vertical_gradient] and [#lad_vertical_gradient_level lad_vertical_gradient_level]. |
| 196 | | }}} |
| 197 | | |---------------- |
| 198 | | {{{#!td style="vertical-align:top" |
| 199 | | [=#plant_canopy '''plant_canopy'''] |
| 200 | | }}} |
| 201 | | {{{#!td style="vertical-align:top" |
| 202 | | L |
| 203 | | }}} |
| 204 | | {{{#!td style="vertical-align:top" |
| 205 | | .F. |
| 206 | | }}} |
| 207 | | {{{#!td |
| 208 | | Switch for the plant canopy model.\\\\ |
| 209 | | If '''plant_canopy''' is set ''.T.'', the plant canopy model of Watanabe (2004, BLM 112, 307-341) is used.\\ |
| 210 | | The impact of a plant canopy on a turbulent flow is considered by an additional drag term in the momentum equations and an additional sink term in the prognostic equation for the subgrid-scale TKE. These additional terms depend on the leaf drag coefficient (see [#drag_coefficient drag_coefficient]), and the leaf area density (see [#lad_surface lad_surface], [#lad_vertical_gradient lad_vertical_gradient], [#lad_vertical_gradient_level lad_vertical_gradient_level]). The top boundary of the plant canopy is determined by the parameter [#pch_index pch_index]. For all heights equal or larger than zw(k=pch_index), the leaf area density is 0 (i.e. there is no canopy at these heights!).\\ |
| 211 | | By default, a horizontally homogeneous plant canopy is prescribed, if '''plant_canopy''' is set ''.T.''. However, the user can define other types of plant canopies (see [#canopy_mode canopy_mode]).\\\\ |
| 212 | | If '''plant_canopy''' and [#passive_scalar passive_scalar] are set ''.T.'', the canopy acts as an additional scalar source or sink, respectively. The source/sink strength depends on the scalar concentration at the leaf surface, which generally does not vary with time in PALM, and which can be specified with parameter [#leaf_surface_concentration leaf_surface_concentration].\\\\ |
| 213 | | Additional heating by the plant canopy is taken into account, if the default value of parameter [#cthf cthf] is altered in the parameter file. In that case, the value of [#surface_heatflux surface_heatflux] specified in the parameter file is not used in the model. Instead, the near-surface heat flux is derived from an exponential function that depends on the cumulative leaf area index.\\\\ |
| 214 | | '''plant_canopy''' = ''.T.'' is only allowed with a non-zero [#drag_coefficient drag_coefficient]. |
| 215 | | }}} |
| 216 | | |---------------- |
| 217 | | {{{#!td style="vertical-align:top" |
| 218 | | [=#scalar_exchange_coefficient '''scalar_exchange_coefficient'''] |
| | 183 | Above '''pch_index''' the leaf area density (LAD) is automatically set to zero. Up to '''pch_index''' a leaf area density profile can be prescribed in two possible ways:\\\\ |
| | 184 | 1) Creating a piecewise linear LAD-profile by prescribing the parameters [#lad_surface lad_surface], [#lad_vertical_gradient lad_vertical_gradient] and [#lad_vertical_gradient_level lad_vertical_gradient_level].\\\\ |
| | 185 | 2) Employing a beta probability density function for the vertical leaf area distribution, prescribing coefficients [#alpha_lad alpha_lad], [#beta_lad beta_lad] and [#lai_beta lai_beta] (see e.g. Markkanen et al., 2003, BLM 106, 437-459). |
| | 186 | }}} |
| | 187 | |---------------- |
| | 188 | {{{#!td style="vertical-align:top" |
| | 189 | [=#leaf_scalar_exch_coeff '''leaf_scalar_exch_coeff'''] |
