高原夏季西风异常年500 hPa纬向风季节内振荡特征及其与我国降水的关系

利用NCEP/NCAR日平均再分析资料及中国596个测站日降水资料，采用带通滤波、小波功率谱、合成分析、相关分析等方法对青藏高原夏季西风异常年500 hPa纬向风季节内振荡特征及其与我国降水和大气环流的关系进行了分析，结果表明：青藏高原夏季500 hPa纬向风季节内振荡以40～60 d周期为主；该季节内振荡在高原西风异常年份表现出异常的传播特征；且高原西风增强年份，我国30°N~40°N范围内的低频降水与高原低频纬向风几乎为同位相，30°N以南地区的低频降水与高原低频纬向风几乎为反位相，东北地区的低频降水落后于高原低频纬向风约1/4位相；高原西风减弱年份，江淮以北的我国北方大部分地区低频降水与高原低频纬向风几乎同位相，江淮地区的低频降水落后于高原低频纬向风约1/4位相。低频降水与低频环流有较好的配置关系

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

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