江淮流域梅雨期降水与10—30d低频振荡的联系

利用1961--2010年中国756站逐日降水资料和NCEP／NCAR逐日再分析资料，分析了江淮流域梅雨期降水与10～30d低频振荡的关系。结果表明，梅雨偏多年降水具有明显的10～30d的周期变化，低频振荡经向上的北传和纬向上的西传与江淮流域梅雨期降水的活跃及中断关系密切。在梅雨偏多年，低层10～30d振荡主要通过南海低频反气旋和日本海低频气旋对江淮流域降水产生影响，并调控着西太平洋副热带高压的西进、东退，进而影响输送到江淮流域的水汽强度及冷暖空气在江淮流域的汇合；而高层，亚洲大陆中纬度地区东西向的低频气旋和反气旋影响着南亚高压的位置，从而形成江淮流域低频降水的强弱变化。

The relationship between 10 30 d low-frequency oscillation and the rainfall over Changjiang-Huaihe River Valley during Meiyu period

The relationship between 10--30 d low-frequency oscillation and the rainfall over Changjiang-Huaihe River Valley during Meiyu period is analyzed by using the 756 stations＇ daily pre- cipitation data in China and the NCEP/NCAR daily reanalysis data from 1961 to 2010. The results show that a 10--30 d periodic variation is obvious in the flood years during Meiyu period. The activeness and break of rainfall over Changjiang-Huaihe river valley during Meiyu period is also closely associated with the low-frequency oscillations＇ northward and westward propagation. During Meiyu period in flood years, the rainfall over Changjiang-Huaihe river valley is influenced by the low-frequency anticy- clone over the South China Sea and the low-frequency cyclone over the Sea of Japan in the lower tropo- sphere, which modulate the western North Pacific subtropical high to extend westward or to retreat east- ward, and thus affect the water vapor transport and confluence of cold and warm air in Changjiang-Hua- ihe river valley. In the upper troposphere, the low-frequency anticyclone and cyclone in mid-latitude ar- ea over Asian mainland influence the position of South Asian High, which leads to the intensity changes of low-frequency rainfall over Changjiang-Huaihe river valley.