By using the NCEP/NCAR reanalysis data(1°×1°),station precipitation and sounding data on 14—15 July 2006,a study on the effects of dry air in the upper troposphere on Bilis rainstorm in Hunan Province was conducted.The results show that there was a large area of dry air between 500 hPa and 200 hPa before the heavy rain occurred.The dry air weakened and disappeared after the heavy rain occurred.There are some correlations between the dry air and the instable energy.The dry air shifted westward with easterly ...