台风艾云尼非对称降水及动热力结构演变特征分析

Analysis on the asymmetrical precipitation and evolution of dynamic and thermodynamic structure of typhoon Ewiniar

中文关键词:  艾云尼台风  非对称降水  环流背景  结构演变

英文关键词:Typhoon Ewiniar  Asymmetrical precipitation  Circulation background  Evolution of structure

中文摘要:

      台风艾云尼（1804号）第2次登陆广东过程中降水表现出显著的非对称分布，强降水主要位于其路径前进方向的右侧（简称台风右侧）。利用欧洲中期天气预报中心ERA5再分析资料、广东风廓线雷达观测资料以及降水观测资料，对造成非对称降水的环流背景和动力、热力结构演变特征进行了分析。结果表明：艾云尼左右两侧水汽输送及动力、热力条件差异是造成降水非对称的主要原因。加强的低空急流以及台风马力斯（1805号）水汽的输送为台风右侧强降水的产生提供了更好的水汽背景，而低空急流的加强配合高空强的辐散抽吸使得右侧垂直上升运动也明显大于左侧。边界层内强盛的低空急流以及珠江三角洲地区下垫面强摩擦辐合作用导致艾云尼右前侧径向入流强度更强、强入流层厚度更厚、边界层高度更高，且由于距离台风眼墙越近风速越大，上述现象越明显，为强降水的产生提供的动力和水汽条件越好。强降水期间艾云尼右侧低层大气维持不稳定状态，分析表明强低空急流携带的θ_se平流及其随高度的减弱弥补了强降水造成的能量损耗，是不稳定能量维持的重要原因。

英文摘要:

      Before and after the second landing of typhoon Ewiniar (No 1804) in Guangdong, the precipitation showed significant asymmetric distribution characteristics, and heavy precipitation was mainly located on the right side of its path. Based on the reanalysis data of ECMWF ERA5 and wind profiler observations and rainfall observations, the circulation background and evolution characteristics of the dynamic and thermal structures responsible for the asymmetric precipitation are analyzed. The results show that the differences in water vapor transport and dynamic and thermal conditions between the left and right sides of Ewiniar were the main reason for the asymmetric precipitation. The enhanced low-level jet and water vapor transport associated with typhoon Maliksi (No 1805) provided a better water vapor background for the occurrence of heavy rainfall on the right side of the typhoon, and the enhancement of the low-level jet combined with the strong divergence and suction in the upper levels led to significantly larger ascending movement on the right side than on the left side. In the boundary layer, the strong low-level jet and large friction and convergence above the underlying surface of the Pearl River Delta resulted in a stronger radial inflow, a deeper inflow layer and a higher boundary layer in the front right side of Ewiniar. The above phenomenon was more obvious in areas close to the typhoon eye wall, where the wind speed was also large. Therefore, the dynamic and water vapor conditions both were favorable for the generation of heavy rainfall. During the period of heavy rainfall, the lower atmosphere on the right side of Ewiniar remained unstable. Further analysis shows that the strong pseudo equivalent potential temperature advection and its weakening with height made up for the energy loss caused by heavy rainfall, which was an important mechanism for the maintenance of unstable energy.