2020年湖南双季晚稻抽穗扬花期寒露风及大气环流异常特征

Characteristics of Cold Dew Wind and Atmospheric Circulation Anomalies During the Heading and Flowering Stage of Double-cropping Late Rice in Hunan in 2020

利用湖南省97个台站降水、气温资料、NCEP逐日再分析资料,分析了2020年9月湖南严重寒露风天气的时空分布及其同期大气环流的异常特征。结果表明:寒露风始于9月14日,28日基本结束;从发生范围、持续时间、低温强度等特征比较,2020年寒露风略轻于1997年,但强于2002年。西太平洋副热带高压偏强、西伸脊点明显偏西、脊线偏南,850 hPa湖南上空偏南暖湿气流输送较常年异常偏强、盛行上升运动是引起严重寒露风的直接原因。从南海到长江流域有一明显的水汽辐合区,这种水汽输送形势有利于湖南阴雨天气的持续发展,进而造成严重寒露风灾害事件的发生。

Using precipitation, temperature data and NCEP daily reanalysis data from 97stations in Hunan province, the temporal and spatial distribution of severe cold dew winds in Hunan in September 2020 and the anomalous characteristics of atmospheric circulation during the same period were analyzed. The results showed that the cold dew wind started on September 14 and basically ended on September 28;from the comparison of the occurrence range, duration, low temperature intensity and other characteristics, the cold dew wind in 2020 was slightly lighter than that in 1997 but stronger than that in 2002.The western Pacific subtropical high was stronger, the westward extension ridge point was obviously westward, the ridge line was southward, and the 850 hPa southward warm and humid airflow over Hunan was abnormally stronger than normal, and the prevailing upward movement was the direct cause of the severe cold dew wind. From the South China Sea to the Yangtze River Basin, there was an obvious water vapor convergence area. This water vapor transport situation was conducive to the continuous development of the rainy weather in Hunan, which would lead to the occurrence of severe cold dew wind disasters.