Sensitivity of rainfall and submonthly oscillations to moist physical processes schemes on Hainan island in autumn

Abstract

In the autumns of 2010 and 2011, consecutive periods of heavy precipitation occurred in Hainan Island. Two groups of monthly-scale simulation experiments were conducted using the Weather Research and Forecasting model. Sensitivity of rainfall and submonthly oscillations to cumulus parameterization and cloud microphysical schemes were evaluated. Due to that the experiment combining the Tiedtke cumulus parameterization scheme and the WDM6 cloud microphysical scheme could reproduce submonthly oscillation characteristics, which showed the higher skill scores of the precipitation simulation than other experiments. Because the Tiedtke scheme is an overall mass flux convection scheme that describes various types of convection, the Grell-Devenyi scheme does not consider the shallow convection, which affects its simulation performance on submonthly oscillations and rainfall. However, in the same cumulus parameterization scheme, different microphysics schemes also have an impact on simulation performance. Experiments that failed to simulate the characteristics of submonthly oscillations exhibited a lower skill scores of precipitation simulation.Interactions of moist physical processes and submonthly oscillations led to the occurrence and development of two consecutive heavy autumn precipitation events on Hainan Island. Submonthly oscillations resulted in a significant effect on the two strong autumn precipitation events, but dominant frequency modes of submonthly oscillations, oscillation characteristics, and propagation paths differed. The autumn 2010 rainfall was dominated by the 8–15-day quasi-biweekly oscillations. The autumn 2011 rainfall was dominated by the 3–10-day synoptic-scale oscillations.