北大西洋海温在1990年代的变异及其对大气河的影响OA

The authors investigates the variation characteristics of the leading mode of sea surface tem-perature(SST)anomalies in the North Atlantic during 1980-2001 and analyzes its influence on the North Atlantic Oscillation(NAO)and Atmospheric Rivers(ARs).The results indicate that the leading pattern of North Atlantic SST anomalies predominantly exhibits a tripolar structure(North Atlantic Tripole,NAT)during 1980-2001.However,in the early winter of the 1990s,the leading mode shifts to a horseshoe-like pattern(North Atlantic Horseshoe,NAH),which exerts a significant impact on the atmospheric circulation in late winter.Analysis of the physical mechanism reveals that the NAH-like SST anomalies,through the transport of water vapor and heat at the sea-air interface exchange,alter the direction of atmospheric wind fields and moisture transport,which lead to a northward shift in the tracks of ARs.When ARs made landfall in northern Europe,enhanced precipitation-induced diabatic heating over Norway intensified baroclinic instability and storm track activity in this region,further triggering an eastward-shifted NAO anomaly pattern.In contrast,during the early winters of the 1980s,SST anomalies exhibited the NAT-type pattern,and under the influence of abnormally warm SSTs in the Gulf Stream region,the NAO phase rapidly reversed and AR pathways shifted southward.