广州极端降水微物理特征的双偏振雷达研究

Research on microphysical characteristics of extreme precipitation in Guangzhou based on Dual-polarization

利用2017年广州S波段双偏振雷达和地面自动站小时雨量资料,对比分析了广州极端降水(雨强≥50 mm·h^(-1))与强降水(雨强为20~50 mm·h^(-1))的微物理特征。结果表明:极端降水的20 dBZ和30 dBZ回波发展高度与强降水都差异较小,说明广州地区的降水强度与对流发展高度关系不大。在低层,极端降水平均回波更强,雨滴粒径更大,结合Z H-Z DR的分布表明广州地区降水具有海洋性对流特征。与强降水对比,0℃层以下极端降水的Z H、Z DR、K DP值都明显更大,尤其在4~5 km都快速增长,说明广州地区极端降水的发展关键在4~5 km高度,并在下落过程中继续增长,因此造成极端降水的发生。

Using the S-band Dual-polarization radar data and hourly rain gauge data in 2017,the microphysical characteristics of extreme precipitation(more than 50 mm·h^(-1))in Guangzhou are statistically analyzed.A comparative analysis of extreme precipitation and strong precipitation(20-50 mm·h^(-1))is also applied.The results show that there is little difference between the two types of precipitation with respect of 20 dBZ and 30 dBZ echo height,indicating the intensity of precipitation over Guangzhou has little relation with the height of convection.In the lower layer,stronger average echo and larger raindrops can be seen in the extreme precipitation rather than strong precipitation.Combined with the distribution of Z_(H)-Z_(DR),it shows that both types of precipitation over Guangzhou possess characteristics of maritime convection.Compared with strong precipitation,the values of Z_(H),Z_(DR) and K DP of extreme precipitation below 0℃layer are significantly larger,especially at 4-5 km,and they all increase rapidly and continue to increase in the falling process at 4-5 km,indicating that the microphysical processes at 4-5 km are critical to extreme precipitation and thus causing the occurrence of extreme precipitation in Guangzhou.