极端北极反气旋环流的频发加强及其与"暖北极-冷大陆"模态的联系OA

This paper defines the positive anomaly of 500 hPa geopotential height north of 65°N as Arc-tic anticyclonic circulation(AAC).Using the percentile threshold(95th)method,641 days of extreme AAC(EAAC)events are identified.EAAC occurs most frequently and intensely in winter(December to March),showing a significant upward trend,with occurrence days decreasing in the Pacific sector,the Atlantic sector,and the Eurasian sector of the Arctic.The strengthening of EAAC in these sectors and its linkage with the"warm Arctic-cold continents"(WACC)pattern are associated with abnormal upper-level jet stream changes modulating Rossby wave development at middle-high latitudes.In the Pacific sector,weakened zonal winds at the East Asian-North Pacific jet exit enhance the Alaska ridges,leading to"warm Arctic"conditions;cold advection from cut-off lows forms"cold continents".In the North Atlantic,asymmetric zonal wind changes at the jet exit increase cyclonic vorticity,strengthening the Greenland ridges and inducing EAAC and WACC.In Eurasia,a northward-shifted westerly jet and anomalous easterlies promote Rossby wave propagation,enhancing cyclonic vorticity and shifting the polar vortex,thus strengthening EAAC and forming WACC.This study offers a new perspective on Arctic-midlatitude climate linkages.