2006号台风“米克拉”近海急剧增强诊断分析

THE DIAGNOSTIC ANALYSIS ON THE RAPID INTENSIFICATION OF TYPHOON MEKKHALA (2006) OVER OFFSHORE CHINA

关键词:  “米克拉”  近海  急剧增强  深对流云系

Key words:  Mekkhala  offshore  rapid intensification  deep convective cloud system

摘要:

利用ERA-5再分析资料、日本葵花8号卫星黑体亮温资料以及中国气象局上海台风研究所台风最佳路径集资料，对2020年第6号台风“米克拉”（2006）近海强度急剧增强进行诊断分析。（1） 比常年偏暖的29～30 ℃的南海东部海温是“米克拉”急剧增强的有利下垫面条件；200 hPa加强东移的南亚高压、500 hPa加强西伸的副高、低层加强的偏南-西南急流是主要影响系统；相对比深层和高层大气，持续低于4 m/s的低层大气垂直风切是重要因子。（2） “米克拉”的增强主要体现在对流层低层动能的不断增强，在台风急剧增强过程中，中低层的气旋性涡度、低层辐合强度、中高层辐散强度以及上升运动均明显加强；对流层中高层动能在台风急剧增强前的减小可能与增强的高空出流相关。（3） 在“米克拉”急剧增强前，深对流云系强度不断增强，但覆盖面积变化不大；在急剧增强阶段，深对流云系组织的更加紧实集中，覆盖面积明显增大。

Abstract:

Based on the ERA-5 reanalysis data (0.25 °×0.25 °), the hourly black body temperature (TBB) data of the Japanese Himawari-8 satellite, and the best track data provided by Shanghai Typhoon Institute, a diagnostic analysis was made on the rapid intensification(RI) of typhoon Mekkhala (Coded No. 2006) over the offshore region of China. The results are shown as follows. (1) Abnormally high sea surface temperature (SST) of 29 to 30 ℃ in the eastern South China Sea provided favorable underlying surface conditions for the RI of Mekkhala, which occurred under the influencle of the following systems: the South Asia high was strengthening and moving eastward at 200 hPa while the subtropical high was strengthening and moving westward at 500 hPa, and a low-level south-southwest jet was significantly strengthening. Compared with the deep and upper atmosphere, the environmental vertical wind shear(VWS) in the lower atmosphere, which was continuously below 4m/s, was one of the factors causing the RI of Mekkhala. (2) The RI of Mekkhala was mainly reflected in the enhancement of kinetic energy in the lower troposphere. During its RI, cyclonic vorticity in the middle and lower layers, middle-upper-level divergence, low-level convergence and the ascending motion all strengthened significantly. The decrease of kinetic energy in the upper and middle troposphere before the RI might be related to the enhanced upper air outflow. (3) Before the RI of Mekkhala, the intensity of the deep convective cloud system increased, but the coverage area changed little. During its RI, the organization of the deep convective cloud system was more compact and concentrated, and the coverage area expanded obviously.