Circulation variation over western North Pacific and its association with tropical SSTA over Indian Ocean and the Pacific

The circulation variation over western North Pacific and the relationship between circulation and tropical Sea Surface Temperature Anomalies(SSTA) were investigated in this paper.The results showed that western North Pacific anticyclone(WNPAC)/ cyclone(WNPC) is two significantly anomalous phenomena at mid-low troposphere over western North Pacific,and their variation is related to PJ wave line and zonal wave line at mid-high latitude region of Eurasia.Owing to this interrelation,WNPAC/WNPC can influence the climate over East Asian and Eurasia.The result showed also that the relationship between WNPAC/WNPC in summer and SSTA is obviously asymmetrical.Generally,evident WNPAC occur in summer of feeble El Nio years,and are related with warm SSTA in winter of mature El Nio years over equatorial East Pacific and warm SSTA in spring and summer of weakening El Nio years over Indian Ocean,which further display the important bridge role of WNPAC in El Nio event influence on summer climate over East Asian.But the relationship between obvious WNPC and SSTA in Indian Ocean is not steady.The formation and maintenance of WNPAC are mainly related to anomalous westerlies resulting from thermal contrast between SSTA over Indian Ocean and SSTA over the Pacific.The possible cause of asymmetry is further investigated.The results showed that the thermal contrasts between Indo-Pacific in El Nio and La Nia summer are accordant,which possibly result in asymmetry relationship between WNPAC/WNPC and SSTA.