A Simulating Study on Resolvable-Scale Microphysical Parameterization in a Mesoscale Model

The Penn State / NCAR Mesoscale Model (MM5) is used to simulate the precipitation event that occurred during 1-2 May 1994 to the south of the Yangtze River. In five experiments the Kain-Fritschscheme is made use of for the subgrid-scale convective precipitation, but five different resolvable-scalemicrophysicaI parameterisation schemes are employed. They are the simple super-saturation removalscheme, the warm rain scheme of Hsie et al. (1984), the simple ice scheme of Dudhia (1989), the complexmised-phase scheme developed by Reisner et al. (1993), and the GSFC microphysical scheme with graupel.our interest is how the various resolvable-scale schemes affect the domain-averaged precipitation, the precipitation distribution, the sea level pressure, the cloud water and the cloud ice. Through a series of experiments about a warm sector rainfall case, results show that although the different resolvable-scale scheme is used, the differences of the precipitation characteristics among all five runsare not very obvious. However. the precipitation is over-predicted and the strong mesoscale low is producedby the simple super-saturation removal scheme. The warm rain scheme with the inclusion of condensationand evaporation under-predicts the precipitation and allows the cloud water to reach the 3oo hPa level. Thescheme of the addition of graupel increases the resolvableescale precipitation by about 20%-30%. The inclusion of supercooled liquid water in the grid-scale scheme does not affect significantly the results.