NCAR contributions to the Cloud Feedback Model Intercomparison Project (CFMIP)

NCAR's CFMIP/COSP contact: Jen Kay (jenkay at ucar dot edu)
page last updated 1-3-2017

Cloud processes and feedbacks remain the largest uncertainty in climate model projections. As a result, the Cloud Feedback Model Intercomparison Project (CFMIP), an international effort to understand cloud feedbacks and evaluate climate models with observations, was initiated. In collaboration with the university community, NCAR scientists and software engineers have integrated the CFMIP Observation Simulator Package (COSP) into the atmospheric component of NCAR's Community Earth System Model (CESM), the Community Atmosphere Model (CAM). COSP calculates model cloud diagnostics that can be directly compared with satellite observations from ISCCP, CloudSat, CALIOP, MISR, and MODIS. Observations for comparison with COSP diagnostics are available here.

At this time, COSP v1.3 (with local modifications) has been implemented with CAM4 and CAM5 physics and released to the public. The COSP-enabled CAM code has been released for public use with CESM1.0.3, and non-answer changing namelist changes were made for CESM1.0.4. NCAR is providing CFMIP-requested climate model runs with COSP diagnostics in CAM4 and CAM5. Ben Sanderson (NCAR CCR, bsander at ucar dot edu) is in charge of CFMIP runs. Ben Hillman (UW) has made modifications to the AMWG diagnostics package to help with viewing COSP outputs. The COSP-enabled AMWG diagnostics package can be downloaded here. A sample COSP-enabled AMWG diagnostics package comparison of CAM outputs vs. observations is available here. Jen has also run AMIP and coupled runs with CESM1_1_1 on Yellowstone. If you would like restart files or outputs from these runs, please contact Jen.

In preparation for CESM2 and CMIP6, COSP1.4 has been implemented within CAM/CESM. The code is on the CAM trunk and will be released to the public in early 2017 (Date TBD).

More information on:

Repository and code implementation history

COSP outputs available in CAM

COSP namelist options in CAM

What is the easiest way to run COSP within CAM and look at COSP diagnostics using the AMWG diagnostics package?

Running CAM with COSP on Yellowstone.

Related presentations and publications:

English, J. M., Kay, J. E., Gettelman, A., Liu, X., Wang, Y., Zhang, Y. and H. Chepfer, (2014), Contributions of clouds, surface albedos, and mixed-phase ice nucleation schemes to Arctic radiation biases in CAM5, J. Climate, doi:

Kay, J. E., Hillman, B., Klein, S., Zhang, Y., Medeiros, B., Gettelman, G., Pincus, R., Eaton, B., Boyle, J., Marchand, R. and T. Ackerman (2012): Exposing global cloud biases in the Community Atmosphere Model (CAM) using satellite observations and their corresponding instrument simulators, J. Climate, 25, 5190-5207. doi:

Hillman, B. (2012): Evaluating clouds in global climate models using instrument simulators, Masters thesis, University of Washington, Dept. Atmospheric Science.