2019年长江中下游伏秋连旱的异常特征分析

doi:10.3969/j.issn.1673-503X.2021.04.013

摘要/Abstract

摘要：

利用NCEP/NCAR再分析资料及实况观测资料，分析了2019年中国长江中下游地区伏秋连续干旱期间的降水、温度及大气环流异常特征。结果表明：此次干旱具有持续时间长、降水偏少严重、气温较历史同期明显偏高、高温日数明显偏多等极端性特点。西太平洋副热带高压偏强，位置相对偏西、偏北，是形成长江中下游伏秋连旱的最主要原因；南亚高压东伸及负涡度向东输送，利于副热带高压西伸，长江中下游地区始终位于东亚副热带西风急流出口区右侧、对流层中高层负涡度的叠加作用区，使得垂直方向上的下沉辐散得到显著增强；自乌拉尔山至贝加尔湖高压脊形成的"高压坝"，偏弱的极涡和东亚大槽等异常中高纬环流形势稳定维持，使得西风带中的气旋性扰动不易影响到副热带地区，利于西太平洋副热带高压的稳定及干旱的维持；频繁的热带系统活动，使得副热带高压在热带对流加热区以北的负涡度作用下得以进一步加强，并且导致对流层低层西南气流、越赤道气流和东南气流等三支气流在向北的输送路径上发生改变，并使长江中下游地区水汽辐合偏弱，使干旱得以维持。

关键词: 大气环流异常, 西太平洋副热带高压, 热带环流异常

Abstract:

A server drought occurred in the middle and lower reaches of the Yangtze River basin from midsummer to fall in 2019. The characteristics of this abnormal drought were analyzed based on the NCEP/NCAR reanalysis data and meteorological observation data. The results showed that the drought is characterized by a long duration, less precipitation, more rainless day, higher average air temperature, and higher temperature days. The stronger western Pacific subtropical high(WPSA)and its north and west position are the main reason for continuous drought in summer and autumn in the middle and lower reaches of the Yangtze River. The negative vorticity extending eastward and the eastward of the South Asia high are in favour of the western extending of the WPSA. The middle and lower reaches of the Yangtze River are located on the right side of the East Asia subtropical westerly jet exit area and the superposition of negative vorticity in the middle and upper troposphere, which makes the vertical subsidence and divergence significantly enhanced. The dam formed by a high-pressure ridge from the Ural Mountains and Lake Baikal and maintained anomalous middle and high latitude circulation patterns such as the weaker the polar vortex and East Asia trough make it uneasy for the cyclonic disturbance in the westerly belt to affect the subtropical region, which is conducive to the stability of the WPSA and maintenance of drought. In addition, the frequent activities of the tropical system make the subtropical high further strengthened under the negative vorticity in the north of the tropical convective heating area, and leads to the changes of the southwest, cross-equatorial and southeast airflows in the lower troposphere on the northward transport path, and results in the weaker water vapor convergence in the middle and lower reaches of the Yangtze River, thus the drought maintained.

Key words: Atmospheric circulation anomalies, Western Pacific Subtropical High, Tropical circulation anomalies

中图分类号:

P426.616

高琦,徐明. 2019年长江中下游伏秋连旱的异常特征分析[J]. 气象与环境学报, 2021, 37(4): 93-99.

Qi GAO,Ming XU. Characteristics of abnormal continuous drought in summer and autumn in the middle and lower reaches of the Yangtze River in 2019[J]. Journal of Meteorology and Environment, 2021, 37(4): 93-99.

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