湖南夏季降水异常特征及其影响因子

Abnormal Characteristics and Influencing Factors of Summer Precipitation in Hunan

摘要: 利用湖南省32个观测站1960~2013年夏季降水资料和同期NCEP/NCAR提供的再分析资料，分析了湖南夏季降水的年代际变化，异常降水与500 hPa高度场、850 hPa风场、水汽收支的关系。结果表明：湖南夏季降水在1992年和2002年发生了突变；湖南地区夏季降水异常偏少时，500 hPa中高纬地区高度场相对较平直，西太平洋副热带高压偏东偏弱，850 hPa上太平洋海区到华南一带出现大范围的气旋性环流异常，湖南为异常的东北气流控制。降水异常偏多年500 hPa中高纬西高东低形势明显，850 hPa北方为异常反气旋式环流，异常东北风会导致冷空气向南入侵。各边界流入、流出湖南水汽量的多寡会影响湖南夏季降水的多少；西风和南风水汽越强时越利于湖南降水，影响湖南净水汽量最主要的边界是南边界，南边界流入水汽的多少直接关系到湖南夏季降水的多少。

Abstract: Using the 32 observation stations in Hunan Province from 1960 to the summer of 2013 and the reanalysis data provided by NCEP/NCAR in the same period, analyzed the decadal variation of summer precipitation in Hunan Province, and the relationship between abnormal precipitation and 500 hPa height field, 850 hPa wind field, and water vapor balance was studied. The results show that: Hunan summer precipitation mutations occurred in 1992 and 2002; when the summer precipitation in Hunan region is abnormal, height field in the mid to high latitudes at 500 hPa is relatively flat, and the position of the western Pacific subtropical high is eastward and weak. There is a large-scale cyclonic circulation anomaly from the Pacific Ocean to southern China at 850 hPa, and Hunan is controlled by an abnormal northeast airflow. In years with abnormally high precipitation, the high latitudes at 500 hPa show a trend of being higher in the west and lower in the east. The northern part of 850 hPa has an abnormal anticyclonic circulation, and abnormal northeast winds can cause cold air to invade southward. The amount of water vapor flowing into and out of Hunan at each boundary will affect the amount of summer precipitation in Hunan; the stronger the west wind and south wind, the more favorable it is for precipitation in Hunan. The main boundary that affects the net water vapor in Hunan is the southern boundary, and the amount of water vapor flowing into the southern boundary directly affects the amount of summer precipitation in Hunan.