Impact model: CLM4.5

The Community Land Model is the land model for the Community Earth System Model (CESM). It examines the physical, chemical, and biological processes by which terrestrial ecosystems affect and are affected by climate across a variety of spatial and temporal scales. The central theme is that terrestrial ecosystems, through their cycling of energy, water, chemical elements, and trace gases, are important determinants of climate.

Model components consist of: biogeophysics, hydrologic cycle, biogeochemistry and dynamic vegetation.

The land surface is represented by 5 primary sub-grid land cover types (glacier, lake, wetland, urban, vegetated) in each grid cell. The vegetated portion of a grid cell is further divided into patches of plant functional types, each with its own leaf and stem area index and canopy height. Each subgrid land cover type and PFT patch is a separate column for energy and water calculations.

The current version of the Community Land Model is CLM4.5. Simulations for ISIMIP2b were conducted with CLM4.5, and include an interactive Carbon and Nitrogen cycle (CN) and a an interactive crop model (CROP). ISIMIP2a simulations were conducted either with CLM4.0 (global water) or CLM4.5post (agriculture, at 2° resolution).

Water (global)

Information for the model CLM4.5 is provided for the simulation rounds shown in the tabs below. Click on the appropriate tab to get the information for the simulation round you are interested in.

Person responsible for model simulations in this simulation round
Sonia Seneviratne:, 0000-0001-9528-2917, ETH Zurich (Switzerland)
Wim Thiery:, 0000-0002-5183-6145, Vrije Universiteit Brussel and ETH Zurich (Belgium)
Additional persons involved: Wim Thiery
Output Data
Experiments: I, II, III and VIII
Climate Drivers: None
Date: 2018-02-08
Basic information
Model Version: 4.5
Model Output License: CC BY 4.0
Reference Paper: Main Reference: Thiery, W., et al. et al. Present-day irrigation mitigates heat extremes. J. Geophys. Res. Atm.,122,1403-1422,2017
Reference Paper: Other References:
Spatial Aggregation: regular grid
Spatial Resolution: 0.5°x0.5°
Temporal Resolution Of Input Data: Climate Variables: subdaily
Temporal Resolution Of Input Data: Co2: annual
Temporal Resolution Of Input Data: Land Use/Land Cover: annual
Temporal Resolution Of Input Data: Soil: constant
Additional Temporal Resolution Information: ISIMIP daily atmospheric input data is temporally disaggregated to 6-hourly meteorological forcing fields for CLM (algorithm courtesy of Guoyong Leng, PNNL)
Input data sets used
Simulated Atmospheric Climate Data Sets Used: IPSL-CM5A-LR, HadGEM2-ES, GFDL-ESM2M, MIROC5
Land Use Data Sets Used: Historical, gridded land use (HYDE 3.2)
Climate Variables: ta, huss, sfcWind, rlds, rsds, pr
Exceptions to Protocol
Exceptions: 1. Atmospheric CO2 concentrations are held constant at 284.7 ppm for picontrol runs (whereas the ISIMIP protocol prescribes 286.38 ppm). Note that this values is only used for the land carbon cycle, i.e. this difference does not affect the atmospheric forcing provided by ISIMIP. CO2 concentrations for the historical simulations follow observations and are consistent with the ISIMIP protocol. 2. Historical simulations are conducted with fixed, present-day land-use (2005soc), this due to the inability of CLM4.5 to account for transient irrigation extend. 3. 365_day calendar instead of proleptic_gregorian 4. For some pixels and time steps negative values were obtained for the variables 'tws', 'qtot', 'qr', 'maxdis', 'mindis', and 'dis'. In those cases, values were forced to be zero. We note however that the occurrence of negative values was very rare, and that values were small whenever they occurred.
Was A Spin-Up Performed?: Yes
Spin-Up Design: picontrol simulations were branched from an existing picontrol spinup run which was run at 1.9° x 2.5° resolution and interpolated to 0.5° x 0.5° resolution using the CESM interpinic tool. Historical simulations were branched from the respective 0.5° x 0.5° ISIMIP picontrol run, scenario runs were branched from the respective 0.5° x 0.5° ISIMIP historical runs
Natural Vegetation
Natural Vegetation Partition: tile approach including 24 PFTs for the vegatated land unit.
Management & Adaptation Measures
Management: Irrigation (see Thiery et al., 2017 for a short description of the irrigation module)
Extreme Events & Disturbances
Key Challenges: Representation of human water management (only irrigation is included in CLM4.5)
Additional Comments: In total >450 variables are stored, additional variables are available upon request (
Technological Progress
Technological Progress: not considered
Soil Layers: 15 soil layers
Water Use
Water-Use Types: Irrigation
Water-Use Sectors: Agriculture
Runoff Routing: Using the MOSART model, See Oleson et al., 2013 for more details
Routing Data: diagnostic tool, conserves water globally
Land Use
Land-Use Change Effects: constant land-use (1860soc and 2005soc)
Dams & Reservoirs
Dam And Reservoir Implementation: absent
Potential Evapotranspiration: absent
Snow Melt: snow model