2019年夏季江南降水偏多的原因分析  

Analysis on the Reasons of More Precipitation in the South of the Yangtze River in Summer of 2019

作　　者：张莹琪 孙即霖[1] 

机构地区：[1]中国海洋大学,山东 青岛

出　　处：《气候变化研究快报》2021年第3期217-227,共11页Climate Change Research Letters

摘　　要：本文利用NECP/NCAR提供的1981~2019年月平均位势高度场、风场、垂直速度场等再分析资料,对2019年夏季中国雨带位置异常偏南的原因进行了分析。研究发现,雨带位置偏南和行星锋区位置异常偏南、强度偏强有很大的关系。造成行星锋区位置异常偏南主要有两个原因:一是位于贝加尔湖附近的高压脊异常偏强,高压脊前的西北气流偏强,冷气团势力偏强将行星锋区推进到江南地区;二是行星锋区南侧西太平洋副热带高压位置的偏南,造成夏季风异常偏弱,暖气团势力相对较弱。副高位置偏南的原因与太平洋发生El Niño事件的次年及印度洋偶极子正位相有关。分别以850 hPa上的垂直速度异常考察行星锋区强迫抬升造成的上升运动异常,以500 hPa上垂直速度异常考察根据热成风原理,行星锋区对应高空西风急流南侧强辐散造成的对流上升运动,发现2019年夏季江南降水主要是由锋面抬升作用引起的。夏季风偏弱导致高空急流南侧对流层中、下层暖湿空气输送偏弱可能是对流性降水作用相对偏弱的原因。Based on the NECP/NCAR reanalysis data of monthly mean geopotential height field, wind field and vertical velocity field from 1981 to 2019, this paper analyzes the reasons for the anomalous southward location of rain belts in China in the summer of 2019. It is found that the southward location of the rain belt is closely related to the anomalous southward location and strong planetary front. There are two main reasons for the anomalous southward position of the planetary front zone. First, the anomalous strong high pressure ridge near Lake Baikal, the strong northwest air flow in front of the high pressure ridge, and the strong cold air mass force pushed the planetary front zone to the south of the Yangtze River. Second, the position of the western Pacific subtropical high on the south side of the planetary front zone is southward, which results in the abnormally weak summer monsoon and relatively weak warm air. The southward location of the subtropical high is related to the next year of El Niño event in the Pacific Ocean and the positive phase of Indian Ocean Dipole. According to the thermal wind principle, the planetary front corresponds to the convective upward movement caused by the strong divergence on the south side of the high-altitude westerly jet. It is found that the summer precipitation over the south of the Yangtze River in 2019 is mainly caused by the frontal uplift. The weak transport of warm and moist air in the middle and lower troposphere on the south side of the upper jet due to the weak summer wind may be the reason why the convective precipitation is relatively weak.

关 键 词：夏季降水 锋面抬升 中亚高压脊 西太平洋副热带高压 

分 类 号：P45[天文地球—大气科学及气象学]