2020年6～7月西南地区东部降水异常偏多的水汽输送特征

利用1961～2020年西南地区东部118个气象站逐日降水量资料和1979～2020年欧洲中期天气预报中心(ECMWF)的ERA5逐月再分析资料以及美国气象环境预报中心和美国国家大气研究中心(NCEP/NCAR)提供的逐6 h全球再分析资料,采用相关、回归、聚类、混合单粒子拉格朗日综合轨迹(HYSPLITv5.0)模型...

Characteristics of Water Vapor Transport Associated with Abnormal Precipitation over the East of Southwestern China in June and July 2020

This paper analyzes the anomalous characteristics of precipitation in the east of southwestern China (ESWC) during June–July 2020 and the related large-scale characteristics of water vapor transport, water vapor budget, and water vapor source using correlation, regression, clustering, hybrid single-particle Lagrangian integrated trajectory (HYSPLITv5.0) model simulation, and other statistical methods based on the daily precipitation data of 118 stations and other reanalysis data. Some indexes of the water vapor intensity in key areas are defined, and the relationship between the water vapor intensity in key areas and sea temperature is investigated. Results show that the average precipitation in the ESWC during June–July 2020 is 50% more than that in the normal year, which is the highest since 1961. Precipitation in most areas is obviously higher than that in the normal year, except for some areas in central Guizhou and northeastern Sichuan. The configuration of the tropospheric atmospheric circulation field during June–July 2020 is a typical rainy circulation situation in the ESWC. At 200 hPa, the position of the upper jet stream leans to the south, and the ESWC is located just south of the jet axis with a strong divergence outflow from the upper layer and a strong convergence inflow from the lower layer, providing favorable dynamic conditions for precipitation. In addition, the western Pacific subtropical high (WPSH) obviously extends westward, and the warm and humid airflow in the southwest side of the WPSH is transported to the ESWC, which is conducive to more precipitation in this region. The quantitative water vapor trajectory tracking results calculated by the Lagrange method show that there are 70.5% of the water vapor paths associated with precipitation in the ESWC during June–July 2020 from the southern routes such as the Bay of Bengal, the South China Sea, and the Arabian Sea, while 17.6% and 11.9% comes from the northern route and the local area, respectively. In the previous winter, the SST (Surface Sea Temperature) of the equatorial Middle East Pacific and the Indian Ocean was relatively high, the WPSH is obviously strong and westward, resulting in the east wind anomaly in the Bay of Bengal and the South China Sea, which is favorable for the westward water vapor transport in the South China Sea but unfavorable for the eastward water vapor transport in the Bay of Bengal. Meanwhile, the anomalous anticyclone from the Philippines to the South China Sea makes the south wind anomaly in the northern part of the Indo-China peninsula, which is conducive to the strong northward water vapor transport in this area. These together resulted in more precipitation in the ESWC.