江淮入梅异常的强信号及其对入梅的影响

Previous Stronger Signal of Anomalous Meiyu Onset over Yangtse-Huaihe River Valley and Its Analysis

江淮入梅具有显著的年际变化特征。利用NCEP/NCAR再分析数据集以及NOAA提供的全球射出长波辐射(OLR)和扩展重建海温(ERSST)等资料,采用相关分析和合成分析等方法研究了江淮入梅异常的前兆强信号,并初步分析了其影响入梅的可能机制。结果表明,ENSO事件是影响江淮入梅早晚较强的前兆信号。前期冬春季出现ENSO暖位相时有利于入梅开始偏晚,ENSO冷位相出现时入梅往往偏早。前期冬季2月和春季Nino4区的海温异常能较好地预测入梅早晚,具有短期气候预测的指示意义和实用性。ENSO暖位相年,亚澳"大陆桥"、菲律宾、西太平洋暖池以及印度半岛附近对流偏弱,不利于西太平洋副热带高压北跳和印度夏季风爆发,东亚地区大气环流季节转换偏晚,入梅因而偏晚;ENSO冷位相年情况则相反。

Meiyu onset over Yangtse-Huaihe river valley is of obvious features of inter-annual vari- ations. Based on NCEP/NCAR reanalysis dataset and NOAA OLR and ERSST data, the previous stronger signal of anomalous Meiyu onset over Yangtse-Huaihe river valley is investigated by employing correlation and composite analyses. Preliminary analyses for the impact of the stronger signal on the Meiyu onset are also studied. The results show that ENSO（Southern Oscillation） events are the previous stronger signal. The Meiyu begins late （early） with the warm （cool） phase of ENSO. The SSTA of Nino4 in February and spring can be regarded as credible implications for forecasting the onset of Meiyu. The weak convective activities around the Asian-Australian “land bridge”, Philippines, the western Pacific warm pool and Indian peninsula correspond with the warm phase of ENSO. The weak convective activities around the regions above-mentioned may not facilitate northward jump of the western Pacific subtropical high and the outbreak of Indian summer monsoon. Consequently, the seasonal transition of atmospheric circulation in the eastern Asian regions is late, which causes the late onset of Meiyu.