On abrupt changes in the general circulation over asian low latitudes around establishing period of asian summer monsoon

In this paper the abrupt changes of the general circulation over the Asian tropical monsoon area during the period of April through June are studied statistically using the 15-year mean NCEP/NCAR reanalysis daily data of 1982-1996.Results show that over the regions of Bay of Bengal and the South China Sea, the abrupt changes in the thickness (averaged temperature) between 500 and 200 hPa levels, the winds at 850 and 200 hPa and the out-going longwave radiation occur in the 4th pentad of May significantly.The quantity of net radiative heating (QRT) at the top of the atmosphere experiences earlier abrupt changes in mid-April and early May.In addition, the circulation abrupt changes occur generally ten days or two weeks later over the Indian monsoon region than over the South China Sea, except for QRT.It usually takes a shorter time period to complete the circulation abrupt changes over the Bay of Bengal and the South China Sea than over Indian monsoon region, with the exception of the high level wind.