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Article Type:
Research Article

COSP: Satellite simulation software for model assessment

A. Bodas-SalcedoMet Office Hadley Centre, Exeter, United Kingdom

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M. J. WebbMet Office Hadley Centre, Exeter, United Kingdom

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S. BonyLaboratoire de Météorologie Dynamique/L'Institut Pierre-Simon Laplace, Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, Paris, France

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H. ChepferLaboratoire de Météorologie Dynamique/L'Institut Pierre-Simon Laplace, Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, Paris, France

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J.-L. DufresneLaboratoire de Météorologie Dynamique/L'Institut Pierre-Simon Laplace, Centre National de la Recherche Scientifique, Université Pierre et Marie Curie, Paris, France

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S. A. KleinProgram For Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Livermore, California

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Y. ZhangProgram For Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Livermore, California

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R. MarchandJoint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, Washington

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J. M. HaynesSchool of Mathematical Sciences, Monash University, Clayton, Victoria, Australia

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R. PincusUniversity of Colorado and NOAA/Earth System Research Laboratory, Boulder, Colorado

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V. O. JohnMet Office Hadley Centre, Exeter, United Kingdom

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Online Publication:
01 Aug 2011
Print Publication:
01 Aug 2011
DOI:
https://doi.org/10.1175/2011BAMS2856.1
Page(s):
1023–1043
Full access

Errors in the simulation of clouds in general circulation models (GCMs) remain a long-standing issue in climate projections, as discussed in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. This highlights the need for developing new analysis techniques to improve our knowledge of the physical processes at the root of these errors. The Cloud Feedback Model Intercomparison Project (CFMIP) pursues this objective, and under that framework the CFMIP Observation Simulator Package (COSP) has been developed. COSP is a flexible software tool that enables the simulation of several satellite-borne active and passive sensor observations from model variables. The flexibility of COSP and a common interface for all sensors facilitates its use in any type of numerical model, from high-resolution cloud-resolving models to the coarser-resolution GCMs assessed by the IPCC, and the scales in between used in weather forecast and regional models. The diversity of model parameterization techniques makes the comparison between model and observations difficult, as some parameterized variables (e.g., cloud fraction) do not have the same meaning in all models. The approach followed in COSP permits models to be evaluated against observations and compared against each other in a more consistent manner. This permits a more detailed diagnosis of the physical processes that govern the behavior of clouds and precipitation in numerical models. The World Climate Research Programme (WCRP) Working Group on Coupled Modelling has recommended the use of COSP in a subset of climate experiments that will be assessed by the next IPCC report. In this article we describe COSP, present some results from its application to numerical models, and discuss future work that will expand its capabilities.

Errors in the simulation of clouds in general circulation models (GCMs) remain a long-standing issue in climate projections, as discussed in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. This highlights the need for developing new analysis techniques to improve our knowledge of the physical processes at the root of these errors. The Cloud Feedback Model Intercomparison Project (CFMIP) pursues this objective, and under that framework the CFMIP Observation Simulator Package (COSP) has been developed. COSP is a flexible software tool that enables the simulation of several satellite-borne active and passive sensor observations from model variables. The flexibility of COSP and a common interface for all sensors facilitates its use in any type of numerical model, from high-resolution cloud-resolving models to the coarser-resolution GCMs assessed by the IPCC, and the scales in between used in weather forecast and regional models. The diversity of model parameterization techniques makes the comparison between model and observations difficult, as some parameterized variables (e.g., cloud fraction) do not have the same meaning in all models. The approach followed in COSP permits models to be evaluated against observations and compared against each other in a more consistent manner. This permits a more detailed diagnosis of the physical processes that govern the behavior of clouds and precipitation in numerical models. The World Climate Research Programme (WCRP) Working Group on Coupled Modelling has recommended the use of COSP in a subset of climate experiments that will be assessed by the next IPCC report. In this article we describe COSP, present some results from its application to numerical models, and discuss future work that will expand its capabilities.

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