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24, chemin de Borde Rouge -Auzeville - CS52627 31326 Castanet Tolosan cedex - France

Last update: May 2021

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AGADAPT - Adapting the water use by the agriculture sector

Biophysical Model

Community Land Model - CLM

In AGADAPT, the well developed and versatile Community Land Model (CLM) (version 4.0) was used to model the water and energy balance of a field site with Citrus trees. The Community Land Model, developed by the National Center for Atmospheric Research (NCAR) calculates soil moisture and evapotranspiration (Oleson et al., 2013). CLM uses the simplified Richards equation to model water flow in the unsaturated zone and for the calculation of the land surface fluxes the Monin-Obukhov similarity theory is invoked. The land cover is represented by 17 plant functional types (PFTs) and the calculation of surface fluxes is based on these PFTs. CLM derives soil hydraulic and thermal parameters on the basis of sand fraction, clay fraction and organic matter density. The following processes are simulated by CLM in the context of the AGADAPT project and real-time optimization of irrigation amounts: transfer of solar radiation and longwave radiation; momentum, sensible heat and latent heat fluxes; soil hydrology; stomatal physiology and photosynthesis; crop dynamics and irrigation (Oleson et al., 2013).

You can download the PDF Version here

Model description

CLM contains modules for the following land surface processes:

  • Vegetation composition, structure, and phenology
  • Absorption, reflection, and transmittance of solar radiation
  • Absorption and emission of longwave radiation
  • Momentum, sensible heat (ground and canopy), and latent heat (ground evaporation, canopy evaporation, transpiration) fluxes
  • Canopy hydrology (interception, throughfall, and drip)
  • Soil hydrology (surface runoff, infiltration, redistribution of water within the

column, sub-surface drainage, groundwater)

  • Stomatal physiology and photosynthesis

Figure 1. CLM components (

Model inputs

Input Type

Variable identification and metric

Temporal scale

Data source

Atmospheric forcing

incident longwave (W/m2)   

incident solar (W/m2)   

precipitation (mm/s)   

pressure at the lowest level (Pa)   

relative humidity at the lowest level (%)

temperature at the lowest level (K)   

wind at the lowest level (m/s)




sand fraction (%)

clay fraction (%)

organic matter density (Kg/m3)




Vegetation type

Root distribution parameters


CLM default

Leaf Area Index

The citrus leaf area index was calculated based on the ground coverage (fcover%)

LAI  = -1.3*Log(1-fcover%/100)/(1+fcover%/100)




Model outputs

Output variable




canopy transpiration



canopy evaporation



ground evaporation



total evaporation



ground evaporation



canopy evaporation



canopy transpiration



qflx_evap_soi + qflx_evap_veg + qflx_tran_veg

mm H2O/s


Potential Evapotranspiration

mm H2O/s


atmospheric rain



atmospheric snow



total water storage (unsaturated soil water + groundwater)



volumetric soil water



soil liquid water



surface runoff



total liquid runoff (does not include QSNWCPICE)



sub-surface drainage



soil water potential in each soil layer



Condition of access to the model codes


  • Software is available to be used; CLM4.0 can be used freely (this was also checked with NCAR/UCAR), for the developed data assimilation routines a licensing condition will be followed.
  • Costs: to be agreed upon.
  • Contact: Prof. Dr. Harrie-Jan Hendricks-Franssen (



Oleson, K., et al. (2013). "Technical Description of version 4.5 of the Community Land Model (CLM)." Ncar Technical Note NCAR/TN-503+STR, National Center for Atmospheric Research, Boulder, CO, 422 pp.

CLM description PDF

Read more