Abstract:

Using the wavelet power spectrum,bandpass filter,correlation and composition analysis,the intraseasonal oscillation of 500 hPa zonal wind in the abnormal years of the westly wind in summer over the Tibetan Plateau,and its relationship to the precipitation in China were studied,based on the daily NCAR/NCEP reanalysis and the daily precipitation data from 596 stations in China.The results reveal that:the 40-60 day oscillation had important contributions to the intraseasonal oscillation of the 500 hPa zonal wind in summer on the Tibetan Plateau,and they showed different propagation characteristic in the abnormal years of the zonal wind over the Tibetan Plateau.During strengthening years in westerly wind,the phase of precipitation in the 30°N~40°N of China covering 40~60 d time scale well agreed with that of the zonal wind on the Tibetan Plateau,but the low frequency precipitation in the south of 30°N of China and the low frequency zonal wind on the Tibetan Plateau were nearly out of phase to each other.And the low frequency precipitation in the northeastern area droped behind the low frequency zonal wind about a quarter of phase.During weakening years in westerly wind,the low frequency precipitation in the north of the Jianghuai Region well agreed with that of the zonal wind on the Tibetan Plateau,and the low frequency precipitation in the Jianghuai Region droped behind the low frequency zonal wind about a quarter of phase.Meanwhile,relatively significant relationships were found between low frequency precipitation and low frequency circulation