“碧利斯”(0604)暴雨过程不同类型降水云微物理特征分析

本文利用"碧利斯"(0604)暴雨增幅过程高分辨率的数值模拟资料, 将降水分成对流降水和层云降水, 对比分析了不同类型降水云微物理特征和过程的差异, 探讨了不同类型降水对暴雨增幅的贡献, 结果指出:(1)暴雨增幅前, 降水基本为层云降水, 对流降水只存在于零星的几个小区域, 暴雨增幅发生时段, 对流降水所占比例较暴雨增幅前有显著增加, 平均降水强度达层云降水强度的3倍多。(2)暴雨增幅时段, 云系发展更加旺盛, 云中各种水凝物含量较增幅前明显增加, 其中, 对流和层云降水区云中水凝物含量均有一定程度增长, 但对流降水区增加更显著;而无论增幅前还是增幅时段, 对流降水区云中水凝物含量均要明显大于层云降水区, 并且两者的这种差异随着地面降水强度的增强而增大。(3)暴雨增幅前后, 对流降水区雨滴的两个主要来源最终均可以追踪到云水, 通过云水与大的液相粒子(雨滴)和大的固相粒子(雪)之间、以及大的固相粒子(雪和霰)之间的相互作用和转化, 造成雨滴增长, 并最终形成地面降水, 而层云降水区中与雨滴形成相关的上述主要云微物理过程明显变弱, 但层云降水区中暴雨增幅时段的上述过程又要强于增幅前, 说明层云降水对暴雨增幅也有一定贡献。

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.