Circulation Variation Over the Western North Pacific and Its Association with Tropical Ssta Over the Indian Ocean and the Pacific

Abstract

AbstractThe circulation variation over the western North Pacific and its relationship between circulation and tropical SSTA were investigated in this paper. The results show that western North Pacific (WNP) anticyclone/cyclone are two significantly anomalous phenomena at mid‐low troposphere over WNP, and their variation is related to PJ wave line and zonal wave line at mid‐high latitudes of Eurasia. Owing to this interrelation, WNP anticyclone/cyclone can influence the climate over East Asia and Eurasia. The results also show that the relationship between WNP anticyclone/cyclone in summer and SSTA is obviously asymmetric. Generally, evident WNP anticyclone occurs in summer of feeble El Niño years, related with warm SSTA in winter of mature El Niño years over the equatorial east Pacific and warm SSTA in spring and summer of weakening El Niño years over the Indian Ocean, which further displays that the WNP anticyclone plays an important bridge role in El Niño event influence on summer climate over East Asia. But the relationship between the obvious WNP cyclone and SSTA in the Indian Ocean is not steady. The formation and maintain of WNP anticyclone are mainly related to anomalous westerlies resulting from thermal contrast between SSTA over the Indian Ocean and SSTA over the Pacific. The possible cause of asymmetry is further investigated. The results show that the thermal contrasts between Indo‐Pacific in El Niño and La Niña summer are accordant, which possibly results in asymmetric relationship between WNP anticyclone/cyclone and SSTA.