The Relationship Between Summer Cross Equator Flows And ENSO And China Summer Rainfall

The features of interannual relationships and the decadal variabilities of interannual relationships between summer 850hPa cross equator flows of eastern hemisphere and ENSO and China summer rainfall are analyzed by using NCEP/NCAR reanalysis data, sea surface temperatures data of Hadley Center and rainfall data of 160 stations of China. Results show that:There are 5 cross equator flows channels in the eastern hemisphere. They are 45 E,90 E,105 E, 125 Eand 150 E.Mascarene High is weaker(stronger) and Australia High is stronger(weaker) than normal in the El Nino(La Nina) years, which cause summer 850hPa Somali jet weaker(stronger) and the cross equator flows of 90 E, 105 E, 125 E and 150 E are stronger(weaker) than normal in the El Nifio(La Nina) years. The strong cross equator flows of 90 E, 105 E, 125 E and 150 E and weak Somali jet will cause the western wind anomolis breaking out in the western equator Pacific, which will be in favor of the arising of ENSO events.The interannual relationship between Somali jet and ENSO has broken down in the late 1970s while the interannual relationships between the cross equator flows of 105 E, 125 E and 150 E and ENSO have strengthened in the late 1960s. The eastward shift in the Walker circulation and western wind anomolis are the possible reasons of the change of relationships between summer cross equator flows and ENSO.East Asia summer monsoon is stronger when the cross equator flow of 90 E is stronger than normal. The East Asia summer monsoon anomoly can affect the atmosphere circulation and climate in the East Asia and Pacific Ocean regions through the western Pacific subtropical anticyclone and the EPA wavetrain. In thestrong cross equator flow of 90 E years, there has more precipitation in the middle and lower reaches of Yangtze river valley regions while there has less precipitation in the northeast China regions. Vice versa.The interannual relationship between summer low level cross equator flow of 90 E and the precipitation of China has strenthened in the late 1970s. The possible reason is the relationship between the summer low level cross flow of 90 E and 500hPa height has strenthened in the late 1970s.