ABRUPT CHANGE IN ELEMENTS AROUND 1998 SCS SUMMER MONSOON ESTABLISHMENT WITH ANALYSIS OF ITS CHARACTERISTIC PROCESS

The latest dataset from the SCS(South China Sea)Monsoon Experiment is used to investigatethe features of abrupt change in some meteorological elements before,during and after the summermonsoon’s establishment in 1998 and explore its onset characteristic process.We have arrived at apreliminary conclusion that the 1998 Asian summer monsoon is established first in the SCS as earlyas May 23,which is representative of the earliest indicator of the conversion from a winter into asummer monsoon situation in Asia;the continued retreat eastward of the western Pacificsubtropical high from the SCS region has direct effect on the SCS summer monsoon establishmentbecause the withdrawal favors the release of unstable energy,responsible for the sudden onset ofthe monsoon.Our tentative investigation indicates that the eastward extension of the westerly andrainfall band from the equatorial Indian Ocean into the Indo-China Peninsula and the southwardspreading of an active South-China stationary front,acting as the interaction between mid and lowlatitude systems,are likely to be the characteristic events contributing to the subtropical high’seastward retreating and the summer monsoon’s onset over the SCS.