Characteristics of the anomalous northward jump of the western Pacific subtropical high during midsummer and its climate impact
Based on the ERA5 reanalysis data from 1979 to 2021,this study investigated the characteristics of the anomalous northward jump of the Western Pacific Subtropical High(WPSH)during midsummer and analyzed the influence of the tropical Intraseasonal Oscillation(ISO)originating from various sources on the anomaly.The climatic effects of the anomalous WPSH northward jump during summertime over eastern China were also discussed.When the northward jump occurs earlier than normal,during the three leading pentads before the northward jump,there is a notable suppression of low-frequency convection over the Maritime Continent and tropical western Pacific,which gradually propagates northward and northwestward before the northward jump.In the meantime,a negative low-frequency diabatic heating anomaly propagates to the subtropics.The above factors result in positive geopotential height anomalies over the mid-latitude western Pacific,favoring the WPSH northward jump during midsummer.When the northward jump occurs later than normal,during the three leading pentads before the northward jump,there is an intensified suppression of low-frequency convection over the subtropical western Pacific,and it propagates northwestward.The negative diabatic heating anomaly over.the tropical western Pacific also propagates northwestward.It excites a low-frequency teleconnection wave train over the North Pacific.The WPSH jumps accompanied by the westward shift of the anomalous mid-latitude anticyclone.In the earlier years,more extremely high temperature events occur over north of the Yangtze River region,and the regions over Northeast,Huanghuai,and Jiangnan are more likely to suffer persistent heavy rainfall.In the later years,the regions over Southwest and Jiangnan are more prone to extremely high temperatures,and the area of middle and lower reaches of the Yangtze River are more likely to suffer more frequent and intense persistent heavy rainfall.
WPSHtropical low-frequency oscillationextremely high temperaturespersistent heavy rainfall
万方数据
维普
