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| NCAR Community Climate System Model | |
|---|---|
| Name | Community Climate System Model |
| Developer | National Center for Atmospheric Research |
| First release | 1990s |
| Latest release | CESM successor models |
| Programming language | Fortran, C, Python |
| Operating system | Unix-like |
| License | Open-source (community codes) |
NCAR Community Climate System Model
The Community Climate System Model is a coupled climate model developed at the National Center for Atmospheric Research for studies spanning atmospheric, oceanic, cryospheric, and land processes. It has been used by researchers at institutions including University Corporation for Atmospheric Research, National Oceanic and Atmospheric Administration, NASA, and many universities for investigations related to IPCC assessments, paleoclimate reconstructions, and regional climate change impacts. Development has been coordinated with international modeling centers such as Met Office, Max Planck Institute for Meteorology, Geophysical Fluid Dynamics Laboratory, and Centre national de recherches météorologiques.
The model integrates atmosphere, ocean, sea ice, and land surface components, enabling simulation of coupled processes relevant to Intergovernmental Panel on Climate Change scenarios, Milankovitch cycles studies, and Last Glacial Maximum experiments. It provides a platform for model intercomparison projects like CMIP and supports experiments referenced in IPCC Assessment Reports and regional downscaling studies linked to CORDEX activities. The CCSM/CESM lineage facilitated interdisciplinary collaborations across Princeton University, Columbia University, Massachusetts Institute of Technology, and Scripps Institution of Oceanography.
Initial development began under funding from the National Science Foundation with contributions from researchers affiliated with NOAA Geophysical Fluid Dynamics Laboratory and university partners. Major versions have included CCSM1, CCSM2, CCSM3, CCSM4 and later transitions to the Community Earth System Model (CESM) with releases coordinated alongside projects at Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, Argonne National Laboratory, and Oak Ridge National Laboratory. Version advances incorporated parameterization updates from groups such as NCAR High Altitude Observatory, NOAA Pacific Marine Environmental Laboratory, and the University of Washington. The model evolution paralleled developments in international efforts at ECMWF and the Japanese Meteorological Agency modeling systems.
Atmospheric physics and dynamics are provided by atmospheric component models informed by schemes used at NCAR Atmospheric Chemistry Division and tested against observations from Mauna Loa Observatory, NOAA ESRL, and Global Precipitation Climatology Project. Ocean circulation is represented by primitive-equation codes with coupling to Scripps Institution of Oceanography datasets and analyses from Argo floats and WOA climatologies. Sea ice modules incorporate thermodynamic and dynamic processes validated against records from NSIDC and expeditions like MOSAiC. Land surface schemes draw on parameterizations developed at University of Arizona and testing with flux tower networks coordinated by FLUXNET. The coupler mediates exchanges following standards used in Earth System Modeling Framework and interoperation practices from OpenMI-aligned projects.
The model has been applied to simulate historical climate variability for periods including the 20th-century, Holocene, and Pliocene. It underpins studies of El Niño–Southern Oscillation, Atlantic Meridional Overturning Circulation, Arctic amplification, and biosphere–climate interactions involving the Amazon rainforest, Sahara Desert, and Boreal forests. Policy-relevant analyses used CCSM/CESM outputs for impacts assessed by IPCC Working Group II and for adaptation planning in programs run by United Nations Environment Programme and World Bank climate units. Paleoceanographic applications linked to sediment core reconstructions from ODP and IODP expeditions have used CCSM-based boundary conditions.
Extensive validation compares model output against observational networks including GHCN, HadCRUT, ERA-Interim, and satellite missions such as MODIS, TRMM, and GRACE. Intercomparison with other models in CMIP5 and CMIP6 has assessed biases in sea surface temperature, precipitation, and top-of-atmosphere radiative fluxes relative to datasets from CERES and ISCCP. Performance improvements targeted energetic balances, cloud radiative effects informed by work at NOAA CICS, and ocean mixing schemes influenced by studies at Woods Hole Oceanographic Institution and Lamont–Doherty Earth Observatory.
Implementation uses scientific languages and libraries common at major computing centers such as NERSC, OLCF, and NCAR-Wyoming Supercomputing Center. The model is parallelized with MPI and supports domain decomposition strategies used at Argonne and Oak Ridge facilities. Workflow and data management integrate with community tools like ESGF for data distribution, CF conventions for metadata, and scripts influenced by Python-based ecosystems developed at University of Chicago and University of Colorado Boulder research groups.
Critiques focus on resolution limits seen in global configurations compared with high-resolution regional systems developed at National Center for Atmospheric Research collaborators and regional modeling groups such as CSU and Penn State. Representation of cloud microphysics, convection, and aerosol–cloud interactions remains an ongoing challenge informed by findings from ARM sites and process studies supported by DOE. Model structural uncertainties are routinely discussed in community workshops attended by researchers from NOAA, NASA GISS, European Centre for Medium-Range Weather Forecasts, and universities like Yale University and University of California, Los Angeles.
Category:Climate models