The Time-space Variation Characteristics Of Cross-equatorial Air Flow And The Relation To China Summer Rainfall And To Tropical Cyclone Frequence In The Northwest Pacific

In this study, we have analyzed the time-space variation characteristics of global cross-equatorial flow(CEF)at the lower and upper rroposphere.especially for the monsoon region of the Eastern Hemisphere. The NCEP/NCAR reanalysis dataset used in this study are from 1958 to 1997. Determined the locations of every cross-equatorial flow channels in the rep/on mentioned above. The relationship between CEF and China summer rainfall and that between CEF and tropical cyclone frequence(TCF) in the Northwest Pacific(NWP) are investigated.lt is found that the several branches of cross-equatorial flow have different interannual variability.periodicity and interdecadal variability.The five channels in the lower troposphere in the monsoon region of the Eastern Hemisphere have different relationships with China summer rainfall .The results also show that there are obvious relation between the interannual variatin of CEF and TCF from July to October in the Northwest Pacific. When the TCF in NWP is high, the Bengal Bay CEF which located at 90 E is strong and the New Guinea CEF located at 150 E is weak;there is a anti-cyclonic circulation near the equator.the equatorial buffer zone is fortified :it is propitious to the equatorial anticyclones activated and push monsoon trough to higher latitude, this circulation pattern can promote the genesis of TC in NWP. These phenomena are relevant to the anomaly low SST in tropic Eastern Pacific (La Nina) and the strengthen of Walker circulation. When TCF is low, the results will be opposite.