## 2.1.2. Biogeophysical and Biogeochemical Processes[¶](#biogeophysical-and-biogeochemical-processes "Permalink to this headline")
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Biogeophysical and biogeochemical processes are simulated for each subgrid land unit, column, and plant functional type (PFT) independently and each subgrid unit maintains its own prognostic variables (see section [2.2.1.1](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#surface-heterogeneity-and-data-structure) for definitions of subgrid units). The same atmospheric forcing is used to force all subgrid units within a grid cell. The surface variables and fluxes required by the atmosphere are obtained by averaging the subgrid quantities weighted by their fractional areas. The processes simulated include ([Figure 2.1.1](#figure-land-processes)):

1.  Surface characterization including land type heterogeneity and ecosystem structure (Chapter [2.2](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Ecosystem/CLM50_Tech_Note_Ecosystem.html#rst-surface-characterization-vertical-discretization-and-model-input-requirements))
    
2.  Absorption, reflection, and transmittance of solar radiation (Chapter [2.3](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Surface_Albedos/CLM50_Tech_Note_Surface_Albedos.html#rst-surface-albedos), [2.4](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Radiative_Fluxes/CLM50_Tech_Note_Radiative_Fluxes.html#rst-radiative-fluxes))
    
3.  Absorption and emission of longwave radiation (Chapter [2.4](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Radiative_Fluxes/CLM50_Tech_Note_Radiative_Fluxes.html#rst-radiative-fluxes))
    
4.  Momentum, sensible heat (ground and canopy), and latent heat (ground evaporation, canopy evaporation, transpiration) fluxes (Chapter [2.5](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#rst-momentum-sensible-heat-and-latent-heat-fluxes))
    
5.  Heat transfer in soil and snow including phase change (Chapter [2.6](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Soil_Snow_Temperatures/CLM50_Tech_Note_Soil_Snow_Temperatures.html#rst-soil-and-snow-temperatures))
    
6.  Canopy hydrology (interception, throughfall, and drip) (Chapter [2.7](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Hydrology/CLM50_Tech_Note_Hydrology.html#rst-hydrology))
    
7.  Soil hydrology (surface runoff, infiltration, redistribution of water within the column, sub-surface drainage, groundwater) (Chapter [2.7](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Hydrology/CLM50_Tech_Note_Hydrology.html#rst-hydrology))
    
8.  Snow hydrology (snow accumulation and melt, compaction, water transfer between snow layers) (Chapter [2.8](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Snow_Hydrology/CLM50_Tech_Note_Snow_Hydrology.html#rst-snow-hydrology))
    
9.  Stomatal physiology, photosythetic capacity, and photosynthesis (Chapters [2.9](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Photosynthesis/CLM50_Tech_Note_Photosynthesis.html#rst-stomatal-resistance-and-photosynthesis) and [2.10](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Photosynthetic_Capacity/CLM50_Tech_Note_Photosynthetic_Capacity.html#rst-photosynthetic-capacity))
    
10.  Plant hydraulics (Chapter [2.11](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Plant_Hydraulics/CLM50_Tech_Note_Plant_Hydraulics.html#rst-plant-hydraulics))
    
11.  Lake temperatures and fluxes (Chapter [2.12](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Lake/CLM50_Tech_Note_Lake.html#rst-lake-model))
    
12.  Glacier processes (Chapter [2.13](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Glacier/CLM50_Tech_Note_Glacier.html#rst-glaciers))
    
13.  River routing and river flow (Chapter [2.14](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/MOSART/CLM50_Tech_Note_MOSART.html#rst-river-transport-model-rtm))
    
14.  Urban energy balance and climate (Chapter [2.15](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Urban/CLM50_Tech_Note_Urban.html#rst-urban-model-clmu))
    
15.  Vegetation carbon and nitrogen allocation (Chapter [2.19](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/CN_Allocation/CLM50_Tech_Note_CN_Allocation.html#rst-cn-allocation))
    
16.  Vegetation phenology (Chapter [2.20](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Vegetation_Phenology_Turnover/CLM50_Tech_Note_Vegetation_Phenology_Turnover.html#rst-vegetation-phenology-and-turnover))
    
17.  Plant respiration (Chapter [2.17](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Plant_Respiration/CLM50_Tech_Note_Plant_Respiration.html#rst-plant-respiration))
    
18.  Soil and litter carbon decomposition (Chapter [2.21](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Decomposition/CLM50_Tech_Note_Decomposition.html#rst-decomposition))
    
19.  Fixation and uptake of nitrogen (Chapter [2.18](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/FUN/CLM50_Tech_Note_FUN.html#rst-fun))
    
20.  External nitrogen cycling including deposition, denitrification, leaching, and losses due to fire (Chapter [2.22](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/External_Nitrogen_Cycle/CLM50_Tech_Note_External_Nitrogen_Cycle.html#rst-external-nitrogen-cycle))
    
21.  Plant mortality (Chapter [2.23](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Plant_Mortality/CLM50_Tech_Note_Plant_Mortality.html#rst-plant-mortality))
    
22.  Fire ignition, suppression, spread, and emissions, including natural, deforestation, and agricultural fire (Chapter [2.24](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fire/CLM50_Tech_Note_Fire.html#rst-fire))
    
23.  Methane production, oxidation, and emissions (Chapter [2.25](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Methane/CLM50_Tech_Note_Methane.html#rst-methane-model))
    
24.  Crop dynamics, irrigation, and fertilization (Chapter [2.26](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Crop_Irrigation/CLM50_Tech_Note_Crop_Irrigation.html#rst-crops-and-irrigation))
    
25.  Land cover and land use change including wood harvest (Chapter [2.27](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Transient_Landcover/CLM50_Tech_Note_Transient_Landcover.html#rst-transient-landcover-change))
    
26.  Biogenic volatile organic compound emissions (Chapter [2.29](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/BVOCs/CLM50_Tech_Note_BVOCs.html#rst-biogenic-volatile-organic-compounds-bvocs))
    
27.  Dust mobilization and deposition (Chapter [2.30](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Dust/CLM50_Tech_Note_Dust.html#rst-dust-model))
    
28.  Carbon isotope fractionation (Chapter [2.31](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Isotopes/CLM50_Tech_Note_Isotopes.html#rst-carbon-isotopes))
    

![Image 1: ../../_images/image13.png](https://escomp.github.io/ctsm-docs/versions/master/html/_images/image13.png)

Figure 2.1.1 Land biogeophysical, biogeochemical, and landscape processes simulated by CLM (adapted from [Lawrence et al. (2011)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#lawrenceetal2011) for CLM5.0).[¶](#id1 "Permalink to this image")