春季热带大西洋北部海温异常与我国盛夏降水异常的联系

利用Hadley中心的海表温度资料、全国160站降水资料以及NCEP-DOE AMIP-Ⅱ再分析等资料，运用多种统计分析方法，分析了春季（3—5月）热带大西洋北部海温异常变化特征及其对我国盛夏（7、8月）降水异常的影响。结果表明:春季热带大西洋北部模态是热带大西洋海温异常REOF分解的第一模态，方差贡献率为34.5%。热带大西洋北部海温异常年际变率具有明显的季节差异，其中春季最为显著。春季热带大西洋北部海温异常与我国盛夏华中地区降水异常有显著的正相关关系。进一步分析表明，春季热带大西洋北部的海温正异常可以激发出Rossby波，在热带大西洋西北部和热带东太平洋北部产生异常的气旋式环流，引起上述区域的对流层低层（上层）大气出现异常辐合（辐散），并通过热带大西洋北部地区和太平洋之间的垂直环流异常，在中太平洋地区对流层低层大气出现异常辐散，有利于西北太平洋地区产生异常反气旋式环流，异常反气旋西北侧的西南气流有利于水汽输送至我国华中地区，使该地区降水偏多。且这种影响可以通过热带大西洋北部海温异常的持续性，从春季一直持续到盛夏。 

CHARACTERISTIC OF NORTH TROPICAL ATLANTIC SSTA IN SPRING AND ITS RELATIONSHIP WITH MIDSUMMER PRECIPITATION IN CHINA

Based on the sea surface temperature (SST) data of Hadley Center, the precipitation data of 160 stations in China and the NCEP-DOE AMIP-II reanalysis data, the variability of Northern Tropical Atlantic (NTA) SST anomaly (SSTA) and its association with midsummer precipitation in China are studied by using statistical analysis methods. The results suggest that the NTA mode is the first mode of REOF in the tropical Atlantic SSTA, which reveals 34.5% variance. The NTA SST bears obvious seasonal variability and peaks in spring. The spring NTA SSTA is positively related to midsummer precipitation anomalies in central China. As a Rossby-wave response to the positive NTA SSTA, a low-level (high-level) cyclonic (anticyclonic) is generated over the northwestern NTA and northeastern topical Pacific, with the low-level (high-level) convergence (divergence). As a result, an anomalous low-level divergence is induced over the central Pacific due to the anomalous vertical circulation over the north Atlantic and Pacific, which contributes to inducing an anomalous anticyclone over the subtropical northwest Pacific, the southwesterly airstream of the anomalous anticyclone is conducive to water vapor transport to central China, leading to more precipitation in central China. Because of the continuity of anomalous NTA SSTA, this process can maintain from spring to summer.