HR: 17:20h
AN: A44B-05    [Abstracts]
TI: Recent Improvements to the "Rutledge and Hobbs" Bulk Microphysics Scheme in the GCE Model
AU: * Lang, S E
EM: lang@agnes.gsfc.nasa.gov
AF: SSAI, 10210 Greenbelt Road Suite 600, Lanham, MD 20706, United States
AU: * Lang, S E
EM: lang@agnes.gsfc.nasa.gov
AF: NASA GSFC, Code 613.1, Greenbelt, MD 20771, United States
AU: Tao, W
EM: tao@agnes.gsfc.nasa.gov
AF: NASA GSFC, Code 613.1, Greenbelt, MD 20771, United States
AU: Olson, W
AF: NASA GSFC, Code 613.1, Greenbelt, MD 20771, United States
AU: Olson, W
AF: JCET/UMBC, Department of Geography, Baltimore, MD , United States
AU: Cifelli, R
AF: Colorado St. U., Department of Atmos. Sci., Fort Collins, CO 80523, United States
AU: Braun, S
AF: NASA GSFC, Code 613.1, Greenbelt, MD 20771, United States
AB: The Goddard Cumulus Ensemble (GCE) model is a cloud-resolving model (CRM) and has a variety of different options for cloud microphysics parameterizations. The most commonly used scheme is a bulk 3-class ice scheme wherein the third class of ice is moderate density graupel. This scheme has been and continues to be widely used. However, despite its success and longevity, it has some inherent biases. Recent efforts to improve the scheme have significantly reduced those biases. Comparisons with both ground-based radar data and satellite scattering signatures are used to guide as well as validate the improvements based on two convective cases from TRMM LBA. Qualitative aircraft information is also used as a guide. Initial improvements include eliminating the dry growth of graupel and reducing the efficiency with which cloud particles were collected by snow. Corrections to the Bergerson process resulted in further gains. Finally, adjustments to the saturation scheme, the ice concentration formulation, and properly allowing the sublimation of graupel succeeded in reducing the excessive penetration of 40-dBZ echoes above 10 km. The simulated ppt ice structure after the modifications is far more realistic and in much better agreement with radar and satellite observations. The excessive amount of graupel produced in the base scheme is vastly reduced.
DE: 3314 Convective processes
DE: 3354 Precipitation (1854)
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly