Cloud Microphysical Characteristics of Different Precipitation Types in Bilis (0604) Torrential Rainfall Events

Using high-resolution simulation data of typhoon Bilis (0604), the rainfall was separated into convective and stratiform precipitation. By comparing the cloud microphysical characteristics of the two precipitation types, their contributions to torrential rainfall amplification was assessed and determined as follows: (1) Before precipitation amplification, most precipitation are stratiform, with rainfall in only a few small scattered areas convective. During precipitation amplification, the convective proportion of precipitation increases significantly, with the mean precipitation intensity three times of stratiform precipitation. (2) During precipitation amplification, clouds develop more vigorously and the cloud hydrometeor content increases much more than previously. That is, both convective and stratiform precipitations have characteristic levels of growth of cloud hydrometeors, with a more obvious increase in convective precipitation. Meanwhile, both before and during precipitation amplification, hydrometeors content in convective precipitation is greater than that of stratiform precipitation, with the difference between the two rain types enhanced with increasing of surface precipitation intensity. (3) Before and during precipitation amplification, two main sources of rainfall in the convective precipitation region can eventually be traced back to cloud water. Through the interaction and conversion between cloud water and large liquid particles (rain drops), between cloud water and large solid particles (snow) and between large solid particles (snow and graupel), raindrops grow, ultimately generating surface rainfall. The processes associated with raindrop formation in the stratiform precipitation region are notably weaker. However, these processes in stratiform precipitation during precipitation amplification are stronger than those prior, indicating that stratiform precipitation also contributes to precipitation amplification.