不同密度霰对2008年海南秋季持续性强降水模拟的影响

EFFECTS OF GRAUPEL WITH DIFFERENT DENSITIES ON SIMULATION OF PERSISTENT AUTUMN RAINSTORMS OVER HAINAN ISLAND IN 2008

利用WRF模式对海南2008年秋季持续强降水进行月尺度模拟,并基于WDM6微物理方案研究不同密度霰对强降水模拟及其云微物理过程的影响。结果表明:(1)不同密度霰对降水强度模拟影响较大,LDG(小密度霰)试验海南东部和北部两个降水中心强度减小,HDG(大密度霰)试验东部降水中心强度减小,北部降水强度增大。(2)随着霰密度增大,强降水时期高层霰含量减少,0℃层以下霰含量增多。雨水主要来自霰和雪向雨水的转化,其中霰向雨水转化量最大,对降水贡献最大,并随着霰密度增大霰向雨水转化量增多。(3)随着霰密度增大,暴雨及以下降水范围减小、大暴雨及以上降水范围增大;单位格点降水率增大,大暴雨及以上降水贡献增大。随着降水强度增大,小密度霰收集雨水量增多,霰向雨水净转化量减少,对降水贡献减小;大密度霰融化量明显增多,霰收集雨水量增幅较小,霰向雨水净转化量增大,对降水贡献增大。

In this paper,the WRF model was used to simulate the persistent autumn rainstorms over Hainan Island(HNI)in 2008.The effects of graupel with different densities on the process of heavy rainfall was studied using sensitivity test based on the WDM6 microphysical scheme.The results showed that:(1)Graupel with different densities had significant influence on precipitation intensity.Low-density graupel(LDG)weakened precipitation in the east and north of HNI.High-density graupel(HDG)weakened precipitation in the east of HNI and strengthened precipitation in the north of HNI.(2)As graupel density increased,the amount of graupel decreased in the high altitude area and increased below the 0℃layer.The top two sources of rainwater in these simulations were the conversion of graupel into rainwater and the conversion of snow into rainwater,and the conversion of graupel into rainwater made the largest contribution to precipitation.As graupel density increased,more graupel was converted into rainwater.(3)As graupel density increased,the range of precipitation less than 100mm decreased,and the range of precipitation greater than 100mm increased.As precipitation intensity enhanced,the amount of rainwater collected by LDG increased,the net conversion of graupel into rainwater decreased and its contribution to precipitation decreased.The melting of HDG increased significantly,and the amount of rainwater collected by graupel increased slightly.The net conversion of HDG into rainwater increased,and its contribution to precipitation increased.