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

The latest dataset from the SCS (South China Sea) Monsoon Experiment is used in this paper to study the features of abrupt change in some meteorological elements before, during and after the monsoons establishment in 1998 and to investigate its onset , arriving at preliminary conclusions that the 1998 Asian summer monsoon was established first in the SCS (as early as May 23),and the establishment represented the earliest indicator of conversion from the winter to summer monsoon situation in Asia; the continued eastward retreat of the western Pacific subtropical high from the SCS area had a direct effect on the SCS summer monsoons establishment because the withdrawal favored the release of unstable energy, responsible for the sudden onset of the monsoon. However, why did the subtropical high retreat eastward? This tentative investigation indicates that the interactions between middle and lower latitudes,such as the eastward extension of westerly and rainfall bands from the equatorial Indian ocean to the Indo China and the southward spreading of the active South China stationary front, were likely the characteristic events which contribute to the eastward retreat of the subtropical high and the onset of summer monsoon over the SCS