LOW-FREQUENCY SUMMER MONSOON IN INDONESIA-NORTHERN AUSTRALIA AND ITS RELATION TO CIRCULATIONS IN BOTH HEMISPHERES

摘要

In terms of the expansion by extended empirical orthogonal function (EEOF) with data of ECMWFWMO and of outgoing longwave radiation(OLR) furnished by the NOAA polar-orbiting satellite,a study ismade of November 1981 to March 1982 low-frequency (30--60 day)summer monsoon activity in the Indone-sian-North Australian zone (INAZ) together with its relation to atmospheric circulations in the Northern andSouthern Hemispheres. Results show that at 850 hPa the southward blowing low-frequency NE(SW)wind from the eastern Asiancoast changes, after crossing the euqator, to summer NW (SE) monsoon in the INAZ, which, when convergingwith (diverging from) the western-Australian enforced low-frequency SW (NE) wind, brings about strengthened(weakened) convection in the summer monsoon area and its eastward advance, with corresponding low-frequency variation shown in 850 hPa geopotential height. These outcomes are similar to those from the studyof non-filtered actual observations, leading to the conclusion that the component of low-frequency variationillustrates major features characteristic of the variation in the tropical circulation.