| 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/the/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. |
| 7 | | \\\\\\\\\\\\ |
| 8 | | '''NAMELIST group name: canopy_par''' \\\\ |
| | 4 | The plant canopy model (PCM) 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, BLM 61: 47-64, 1992; Watanabe, BLM 112: 307–341, 2004), and acts as source/sink for heat, humidity, or passive scalar. The presentation [/wiki/doc/tut/the/canopy#Canopymodel "Canopy model"] provides detailed information on canopy-flow theory and the functionality of the canopy model. \\ |
| | 5 | |
| | 6 | The PCM is enabled by adding the NAMELIST {{{canopy_par}}} with appropriate parameters to the INPUT parameter file ({{{<jobname>_p3d}}}), subsequently to the NAMELIST {{{d3par}}}. Available parameters are listed below. \\ |
| | 7 | |
| | 8 | With enabled PCM, the plant canopy by default covers the surface of the entire computational domain (parameter [#canopy_mode canopy_mode] = 'block'). The minimum set of parameters to be used with this mode are: |
| | 9 | * [#canopy_drag_coeff canopy_drag_coeff], [#pch_index pch_index] '''plus''' |
| | 10 | * [#alpha_lad alpha_lad], [#beta_lad beta_lad], [#lai_beta lai_beta] '''or''' |
| | 11 | * [#lad_surface lad_surface], [#lad_vertical_gradient lad_vertical_gradient], [#lad_vertical_gradient_level lad_vertical_gradient_level], |
| | 12 | to prescribe the vertical distribution of leaf area density. \\ |
| | 13 | Alternatively, the plant canopy can be three-dimensionally customized, by either providing: |
| | 14 | * a NetCDF input file ({{{<jobname>_static}}}, in same location as {{{<jobname>_p3d}}}, available from r2746) with 3D information of leaf area density '''or''' |
| | 15 | * user-defined code (see [wiki:doc/app/userint user interface guide], and subroutine {{{user_init_plant_canopy.f90}}} under {{{trunk/SOURCE}}} directory) |
| | 16 | The attached plant-canopy example setup [attachment:? test_canopy] includes: |
| | 17 | * {{{test_canopy_p3d}}}: ASCII parameter file |
| | 18 | * {{{test_canopy_static}}}: NetCDF static-information file with leaf area information (so-called [wiki:doc/app/iofiles/#static static driver] that could also include other information, e.g. topography data) |
| | 19 | * {{{static_driver_generic_canopy_2m.ncl}}}: Simple NCL script that was used to generate the NetCDF file {{{test_canopy_static}}} |
| | 20 | This simulation setup reproduces the results of Shaw & Schumann (BLM 61: 47-64, 1992). |
| | 21 | |
| | 22 | ---- |
| | 23 | '''CAUTION:''' Independently of the method, PALM does not appropriately represent plant canopy on a vertically stretched grid, since this is not intended. We strongly recommend to use grid stretching well above the plant canopy! |
| | 24 | ---- |
| | 25 | |
| | 26 | |
| | 27 | \\\\ |
| | 28 | '''NAMELIST group name: {{{canopy_par}}}''' \\ |
| 65 | | Canopy mode.\\\\ |
| 66 | | Besides using the default value, that will create a horizontally homogeneous plant canopy that extends over the total horizontal extension of the model domain, the user may add code to the user interface (see [#3.5.1 3.5.1]) subroutine {{{user_init_plant_canopy}}} to allow further canopy modes.\\\\ |
| | 99 | Distribution of plant canopy.\\\\ |
| | 100 | Besides using the default value, that will create a horizontally homogeneous plant canopy extending over the total horizontal extension of the model domain, there are two other ways to distribute the plant canopy across the domain. The user may add |
| | 101 | * a NetCDF input file ({{{<jobname>_static}}}, in same location as {{{<jobname>_p3d}}}, available from r2746) with 3D information of leaf area density '''or''' |
| | 102 | * code to PALMs [wiki:doc/app/userint user interface) subroutine {{{user_init_plant_canopy}}} |
| | 103 | to generate customized plant canopy distributions.\\\\ |
| 83 | | Based on '''cthf''', the heat fluxes inside the canopy down to the canopy floor are determined by a decaying exponential function that is dependent on the cumulative leaf_area_index (Shaw and Schumann, 1992, BLM 61, 47-64). At surface grid points without canopy, the surface heat flux is given by parameter [wiki:app/inipar#shf shf]. |
| 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. |
| | 120 | Based on '''cthf''', the heat fluxes inside the canopy down to the canopy floor are determined by a decaying exponential function that is dependent on the cumulative leaf_area_index (Shaw and Schumann, 1992, BLM 61, 47-64). At surface grid points without canopy, the surface heat flux is given by parameter [wiki:app/inipar#surface_heatflux surface_heatflux]. |
