Influence of Graupel/Hail Parameters on the Simulation of a Convective System over Coastal South China in Summer

This paper discusses the effect of graupel/hail parameters on a convective system in Yangjiang, Guangdong Province. The simulation results using the original model settings were similar to observations in terms of radar reflectivity and sea level pressure, as well as the identification of hydrometeor particle classification by X-band dual-polarization radar data. Sensitivity tests using changed parameters of graupel/hail indicated that a size distribution with larger and denser but fewer hail hydrometers resulted in a weaker development of the convective system in the horizontal and vertical directions. With a large terminal velocity of hail, the melting rate of graupel and evaporation rate of rain were the lowest. Hail could reach the ground and the mixing ratio of rain was the largest near the ground. Precipitation, including rainwater and hail, was the largest. However, a size distribution with smaller and lighter but numerous graupel hydrometers resulted in a stronger development of the convective system. The melting rate of graupel and evaporation rate of rain were the largest. More graupel particles were stranded in the air for a longer time—and the maximum mixing ratio of rain was the largest. The precipitation amount, including rainwater only, was the smallest. The changes to graupel parameters also led to differences in microphysical processes.