2019年4月广州白云机场持续暴雨前对流层顶和平流层异常信号分析

利用欧洲中心ERA5再分析资料和广州白云机场自动观测系统降水资料,分析2019年4月白云机场持续暴雨前对流层顶和平流层的信号特征。分析发现,2019年4月中下旬,广州白云机场出现了3次持续时间长、降水量大的持续性暴雨过程,降水较往年同期显著偏多。研究结果表明,3次持续暴雨发生前,对流层顶高度出现了下降,平流层高位涡冷空气入侵,机场上空位涡升高;在环流场中,中低纬地区对流层顶和平流层东风偏强,向北和向下传播,广州白云机场终端区在暴雨发生前西风持续下传;广州白云机场上空暴雨发生前对流层顶至平流层位势高度正异常。暴雨发生前,平流层冷空气高位涡移入、对流层顶下降、西风的下传均有利于持续性暴雨的生成。

Analysis of Tropopause and Stratospheric Anomaly Signals before Persistent Rainstorm at Baiyun Airport in April 2019

The signal characteristics of the tropopause and stratosphere before the continuous heavy rain at Baiyun Airport in April 2019 are analyzed through the European Center ERA5 reanalysis data and the precipitation data from the automatic observation system of Guangzhou Baiyun Airport. The analysis finds out that in mid-to-late April 2019, Guangzhou Baiyun Airport experienced three continuous heavy rains with long duration and large precipitation which was significantly higher than the same period in previous years. The results show that before the occurrence of the three continuous heavy rains, the height of the tropopause dropped, the high-potential vorticity cold air in the stratosphere invaded, and the vacant potential vorticity above the airport increased. In the circulation field, the easterly winds at the top of the troposphere and stratosphere were stronger in the middle and low latitudes, spreading northward and downward. Before the heavy rain occurred, the westerly wind continued to spread down from the terminal area of Guangzhou Baiyun Airport, and the tropopause to stratospheric height was positively abnormal. When the high potential vorticity of cold air in the stratosphere moved in, the tropopause fell, and the westerly wind propagated down, continuous heavy rains are easier to occur.