一次青藏高原低涡影响下的云-降水宏微观特征研究

Macro-microscopic Characteristics of Cloud-precipitation under the Influence of a Low Vortex over the Tibetan Plateau

为进一步认识高原低涡影响下云-降水的垂直结构和微物理特征,利用那曲毫米波雷达和雨滴谱仪资料,结合ERA-5再分析和FY-2G卫星资料,对2015年8月17-19日一次高原涡云系的天气背景、雷达回波和相关物理量进行分析。结果表明,18日凌晨高原涡发展达到最强,那曲上空对流云发展旺盛;随后,强度逐渐减弱,那曲上空过渡为层积云;至19日20时,高原涡减弱消散。此次高原涡降水包含对流云降水和层积云降水,前者回波呈火焰状的上冲结构,回波强度达30 dBZ,但持续时间短,距离地面1 km处存在明显回波亮带;后者在回波图上多为片状,雷达回波强度在20 dBZ以下,持续时间较长。两类降水的雨滴谱存在显著差异,对流云降水粒子直径更大、雨滴谱更宽。

To further understand the vertical structure and microphysical characteristics of cloud-precipitation under the influence of low plateau vortex,the weather background,radar echo and related physical quantities of a plateau vortex cloud system were analyzed on August 17-19,2015 and analyzed by Naqu millimeter wave radar and raindrops spectrometer,combined with ERA-5 reanalysis and FY-2G satellite data.The results show that the plateau vortex reaches its strongest in the early morning of the 18th,and the convective cloud development over Nagqu is vigorous;then,the strength gradually weakens and it passes into cumulus;by 20:00 on the 19th,the plateau vortex weakened and dissipated.The plateau vortex precipitation includes convective cloud precipitation and cumulus precipitation.The former has a flame-like upward structure with echo intensity reaching 30 dBZ,but the duration is short,with an obvious echo bright belt at 1 km above the ground;the latter is mostly sheet on the echo chart,with radar echo intensity below 20 dBZ and long duration.The drop profiles differ significantly between the two types of precipitation,with a larger diameter of convective cloud precipitation particles and a wider droplet spectrum.