Impact of different cumulus parameterizations on the numerical simulation of rain over southern China

The effect of cumulus parameterizations on the numerical simulation of rain over southern China, which is a subtropical coastal area, is studied by considering two typical cases of rain in the region, namely, showers in association with a surface trough of low pressure, and outer rain band of a tropical cyclone. The Regional Atmospheric Modelling System (RAMS) version 4.4 is used at a horizontal resolution of about 10 km for which cumulus parameterization could be used. The numerical experiments include: (a) without the use of cumulus parameterization, (b) without the use of cumulus parameterization and with cloud-top turbulent mixing switched off (similar to the squall line study by Szeto and Chan (2006)), (c) Kuo cumulus parameterization, (d) the standard Kain-Fritsch (KF) cumulus scheme of RAMS, and (e) the modified KF scheme of Truong et al. (2007). Based on the study results of these typical cases, it appears that method (b) is the best in simulating the intense mesoscale convection in the rain events. On the other hand, the rain given by the modified KF scheme in (e) in general appears to be too weak in comparison with weather radar observations.