| Abstract: | By using data of serially numbered typhoons in northwestern Pacific and NOAA OLR data andNCEP/NCAR reanalysis data of wind field, based on the statistics and study of the relationship between thecalendar years with more (or fewer) summer typhoons and ENSO events, we compared the composites of OLReigenvectors and tropical summer wind fields during El Nino and La Nina events with more or fewer thannormal summer typhoons, respectively. The results show that, in summer, without remarkable systematicanomalies of Mascarene High and Australia High in South Hemisphere, the anomaly of Walker circulation willdominate and follow the rule of ENSO impacts to atmospheric circulation and typhoon frequency. Otherwise,when systematic anomalies of Australia High appear during the El Nino events, circulation anomalies in theSouth Hemisphere will dominate, and many more typhoons will occur. In 1999, which is a special year of LaNina events, northward and eastward monsoon was induced by the stronger Mascarene High, and fewertyphoons arose. The typhoon source are regions where weak vertical wind shear, warm pool in western Pacificand the area with monsoon troughs are overlapping with each other. Finally, this paper analyzes and comparesthe source locations and ranges of more (fewer) typhoons in the events of El Nino and La Nina, respectively. |
