2005年6月东亚夏季风活动异常及其影响机制初步分析

STUDY ON THE ANOMALY OF THE EAST ASIAN SUMMER MONSOON IN JUNE 2005 AND THE AFFECTING MECHANISM

应用欧洲中心(ECMWF)逐日08时客观分析资料、中国测站降水资料、OLR资料和NCEP2再分析资料以及国家气象中心提供的1976～2006年的逐日西太平洋副热带高压脊线位置,利用合成分析、小波分析和带通滤波等方法,初步分析了2005年东亚夏季风的活动特征和影响机制。结果发现2005年6月东亚夏季风活动出现明显异常,其中31～32候季风前沿异常停留在南海-菲律宾一带以及华南西部,33～35候季风前沿停滞在华南地区,较常年明显偏南,造成了我国华南洪涝;36候季风前沿跳至黄淮地区,导致长江空梅、黄淮地区多雨。进一步研究发现西太平洋副热带高压和中高纬槽脊活动异常及热带和中高纬度低频振荡是导致2005年6月东亚夏季风异常的主要原因。

Using objective analysis data of European Centre for Medium-Range Weather Forecasts （ECMWF）, the observed daily precipitation data from stations over China, NCEP/NOAA reanalysis data, the Outgoing Longwave Radiation （OLR） data and the daily location of the subtropical high provided by National Meteorological Center, and by the means of composite analysis, wavelet analysis and band pass filter, we analyzed the movement of the East Asian summer monsoon （EASM） in 2005 and the Influencing Mechanism. We found that the EASM was abnormal in June 2005. During the 31Stand 32no pentad, the front of EASM stayed abnormally over the South China Sea, the Philippines and the western South China. The front kept staying over South China during the 33^rd - 35^th pentad, with the position of the front being more southward than normal, bringing heavy storms to South China. But the front of EASM jumped to the valleys of Yellow River and Huaihe River at the 36^th pentad and it didn＇t stay over the Yangtze River in 2005. So this caused Meiyu （sustaining rain） to occur outside the river valley and brought more rain in the valleys of Yellow River and Huaihe River. We make further study and found out that the anomaly of EASM was caused by the unusual movement of the trough and ridge over the middle and high latitudes, the subtropical high over the Northwestern Pacific and ISO （the intraseasonal oscillation） from the tropics and middle and high latitude.