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Development of Two-Moment Cloud Microphysics for Liquid and Ice Within the NASA Goddard Earth Observing System Model (GEOS-5)This work presents the development of a two-moment cloud microphysics scheme within the version 5 of the NASA Goddard Earth Observing System (GEOS-5). The scheme includes the implementation of a comprehensive stratiform microphysics module, a new cloud coverage scheme that allows ice supersaturation and a new microphysics module embedded within the moist convection parameterization of GEOS-5. Comprehensive physically-based descriptions of ice nucleation, including homogeneous and heterogeneous freezing, and liquid droplet activation are implemented to describe the formation of cloud particles in stratiform clouds and convective cumulus. The effect of preexisting ice crystals on the formation of cirrus clouds is also accounted for. A new parameterization of the subgrid scale vertical velocity distribution accounting for turbulence and gravity wave motion is developed. The implementation of the new microphysics significantly improves the representation of liquid water and ice in GEOS-5. Evaluation of the model shows agreement of the simulated droplet and ice crystal effective and volumetric radius with satellite retrievals and in situ observations. The simulated global distribution of supersaturation is also in agreement with observations. It was found that when using the new microphysics the fraction of condensate that remains as liquid follows a sigmoidal increase with temperature which differs from the linear increase assumed in most models and is in better agreement with available observations. The performance of the new microphysics in reproducing the observed total cloud fraction, longwave and shortwave cloud forcing, and total precipitation is similar to the operational version of GEOS-5 and in agreement with satellite retrievals. However the new microphysics tends to underestimate the coverage of persistent low level stratocumulus. Sensitivity studies showed that the simulated cloud properties are robust to moderate variation in cloud microphysical parameters. However significant sensitivity in ice cloud properties was found to variation in the dispersion of the ice crystal size distribution and the critical size for ice autoconversion. The implementation of the new microphysics leads to a more realistic representation of cloud processes in GEOS-5 and allows the linkage of cloud properties to aerosol emissions.
Document ID
20140013016
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Barahona, Donifan
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Molod, Andrea M.
(Maryland Univ. College Park, MD, United States)
Bacmeister, Julio
(National Center for Atmospheric Research Boulder, CO, United States)
Nenes, Athanasios
(Georgia Inst. of Tech. Atlanta, GA, United States)
Gettelman, Andrew
(National Center for Atmospheric Research Boulder, CO, United States)
Morrison, Hugh
(National Center for Atmospheric Research Boulder, CO, United States)
Phillips, Vaughan,
(Leeds Univ. United Kingdom)
Eichmann, Andrew F.
(Science Systems and Applications, Inc. Lanham, MD, United States)
Date Acquired
October 15, 2014
Publication Date
September 4, 2013
Publication Information
Publisher: European Geosciences Union
Subject Category
Geosciences (General)
Report/Patent Number
GSFC-E-DAA-TN11166
Funding Number(s)
CONTRACT_GRANT: NNG12HP06C
CONTRACT_GRANT: NNX12AD03A
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Aerosol-Cloud Interactions
Clouds
Microphysics
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