Interannual Variation of the Summer Synoptic-Scale Disturbance Activity in the Western Tropical Pacific

Abstract

Abstract The authors computed the occurrence frequency of synoptic-scale disturbances over the western tropical Pacific with a simple synoptic scheme and the Goddard Earth Observing System data for 1980–94 supplemented by the 1979 National Meteorological Center (currently the National Centers for Environmental Prediction) data. The major occurrence of these disturbances exists along the monsoon trough with maximum occurrence frequency over Micronesia. The occurrence frequency distribution undergoes an interannual variation through the influence of large-scale circulation during boreal summer. As a part of the interannual variation of large-scale summer circulation in the Pacific basin, a major anomalous anticyclonic (cyclonic) circulation cell emerges in the western subtropical Pacific (north of 15°N), and a minor anomalous cyclonic (anticyclonic) circulation cell appears in the western tropical Pacific (south of 15°N) during warm (cold) summers. The tropical synoptic-scale disturbance activity is affecte...