淮河流域6-7月涝年降水的10～30 d低频振荡特征

Characteristics of 10- 30 days low-frequency oscillation during flood years from June to July over the Huaihe River Basin

利用1981-2010年全国753站逐日降水资料,NCEP/NCAR逐日再分析资料和NOAA向外长波辐射资料,通过小波分析和Lanczos滤波的方法,得到淮河流域6-7月涝年降水的10～30 d低频振荡特征并进行了分析.结果表明：（1）淮河流域6-7月涝年降水具有明显的10～30 d周期变化.（2）位于高、低空的低频（10～30 d）反气旋和气旋分别影响南亚高压和西太平洋副热带高压的东西进退,从而影响淮河流域的低频降水强度.（3）在850 hPa上,南海上空的低频反气旋（气旋）和日本海地区的低频气旋（反气旋）使得淮河流域有（无）冷暖气流交汇,并随着低频反气旋和气旋向东北方向移动,造成淮河地区低频降水发展为活跃（中断）期.（4）在低频降水过程中,低频OLR负（正）值区域发展加强对应淮河流域降水过程加强（减弱）,当负（正）值区到达淮河流域时,淮河流域降水到达极端活跃（中断）期.随后低频OLR负（正）值区向东移动,淮河流域低频降水过程向过渡期转变.

By using the daily precipitation data during 1981-2010 from 753 stations in China,NCEP/NCAR daily reanalysis data and the Outing Longwave Radiation （OLR） data,the characteristics of 10-30 days low-frequency oscillation during flood years from June to July over the Huaihe River Basin are investigated by the methods of wavelet analysis and Lanczos filter.Results show as follows.（1） 10-30 days variation is obvious in the flood years during June-July over Huaihe River Basin.（2）The 10-30 days low-frequency anticyclone and cyclone in the lower （upper） troposphere modulate the western North Pacific subtropical high （South Asian High） extending westward or retreating eastward,so as to influence the low-frequency precipitation intensity over Huaihe River Basin during the flood years.（3） The lowfrequency anticyclone over the South China Sea and the low-frequency cyclone over the Sea of Japan at 850 hPa contribute to a confluence of cold and warm air over Huaihe River Basin.With their northwarding movement,the low-frequency rainfall in Huaihe River Basin becomes active,vice versa.（4） With the negative （positive） area of the low-frequency OLR extending,the corresponding low-frequency precipitation in the Huaihe River Basin strengthens （weakens） gradually.The low-frequency rainfall becomes active （breaking） when the negative （positive） area covers the Huaihe River Basin.Subsequently,the negative （positive） area moves eastward and the low-frequency rainfall turns to the transition period.