MMM SEMINAR NCAR
A Comparison of Bulk
Microphysical Schemes for Cloud Resolving NWP
NCAR/MMM ASP
Post-Doc
Abstract
The impact of cloud microphysics on cloud resolving simulations is an important issue in numerical weather prediction and regional climate modeling. To investigate the effects of cloud microphysics on WRF forecasts with explicit convection four cases from the BAMEX field phase were simulated with a 4-km WRF using different microphysical schemes, including a sophisticated two-moment five-class scheme. All simulations revealed a surprisingly weak sensitivity to the choice of the microphysical schemes, especially within the first 12 hours of the simulations. For instance, the propagation speed of the convection is almost identical for all microphysical schemes. On the other hand, the schemes produce significantly different cloud structures, e.g. the two-moment scheme is able the distinguish between a narrow line of high reflectivity at the leading edge of the convection and a trailing stratiform region with lower reflectivity while all one-moment schemes favor broad lines of high reflectivity. The choice of the microphysical scheme, or parameters within one scheme, has also a strong effect on the amount of upper level clouds (storm anvils). Compared to observations the Lin scheme overestimates the amount of precipitation in convective regions, while the other schemes give slightly better results.
Wednesday, October 27, 2004,
3:30 PM
NCAR-Foothills
Laboratory
3450 Mitchell Lane
Bldg 2, Rm 1022