亚太地区水汽收支与两类ENSO循环的相互关系及其年代际变化研究

During the past few decades, the dry/wet condition over East Asia-western North Pacific (EA-WNP) has experienced dramatic change, so does ENSO (El-Ni?o and Southern Oscillation) cycle, in particular, with more Central Pacific El-Ni?o (CP ENSO, during which maximum sea surface temperature anomalies exist over tropical central Pacific) and less conventional Eastern Pacific El-Ni?o (EP ENSO, during which maximum sea surface temperature anomalies exist over eastern Pacific) since 1970s. The argument about the different impacts of the two types of ENSO cycle on the climate over EA-WNP remains a hot topic. This study will focus on moisture budget anomaies in association with two types of ENSO cycle (EP-ENSO cycle and CP-ENSO cycle). So far, the following scientific problems have not been sufficiently investigated: What could be changing properties of moisture budget anomalies over EA-WNP during the two types of ENSO cycles including their developing and decaying phases? What could be the mechanism behind the regional water vapor budget responses to the two types of ENSO cycle? How does the ENSO cycle modulate the moisture budget and thus the rainfall on decadal time scale? Scientific answers of these prominent problems can definitely be helpful for enhancing human mitigation of natural hazards and social resilience under the increasing and intensifying impacts of altered climate changes and booming economy and fast population growth.

近年来亚太地区干湿状况发生明显的年代际突变，厄尔尼诺-南方涛动（ENSO）事件作为调控亚太地区气候的重要信号亦发生显著的变化，研究发现ENSO依最大海温异常所在的区域可分为中太平洋型和东太平洋型。自1970s末以来，东太平洋型ENSO循环的发生频率明显减少，而中太平洋型ENSO循环的发生频率则明显增多，关于这两类ENSO循环对亚太气候影响差异的讨论是气象界研究的热点。 本项目以水汽收支作为切入点，定量地、直接地对比两类ENSO循环（东太平洋型ENSO循环与中太平洋型ENSO循环）在其发生、发展及消亡各个阶段，亚太地区的水汽收支存在哪些变异特征，ENSO循环如何通过改变水汽分布及环流异常从而调控亚太地区的水汽收支，进而导致降水的异常。探讨它们的相互关系如何以及这种相互关系在1970s末前后可能发生的变化，揭露ENSO信号对亚太地区降水的预报模型是否发生改变，为亚太地区防灾减灾提供有力保障。

以水汽收支作为切入点，定量地、直接地对比两类ENSO循环（冷舌型ENSO与暖池型ENSO）在其发展、成熟及消亡各个阶段，亚太地区的水汽收支存在哪些变异特征，ENSO循环如何通过改变水汽分布及环流异常从而调控亚太地区的水汽收支，进而导致降水的异常。探讨它们的相互关系如何以及这种相互关系在1970s末前后可能发生的变化，揭露ENSO信号对亚太地区降水的预报模型是否发生改变，为亚太地区防灾减灾提供有力保障。主要结论如下：（1）两类厄尔尼诺不仅表现在暖海温异常的位置上的差异，海温的演变特征、海温异常的幅度亦存在明显差异；（2）两类尔尼诺对东亚气候地区水汽环流的影响存在明显的季节非对称性：暖池型厄尔尼诺的影响主要发生在发展期的夏季；东太平洋型厄尔尼诺的影响在发展期夏季较弱，其影响主要从发展期秋季开始，并不断增强，并持续到消亡期的夏季。（3）中国北部地区在厄尔尼诺发展阶段遭受干旱的可能性更大，消亡阶段则更易遭受洪涝； 东南部和长江流域在厄尔尼诺的成熟及消亡阶段容易遭受洪涝灾害，东南部在消亡期夏季与长江流域相反，更易遭受干旱。这种独特的干旱风险区域模式与调制的 ENSO 在不同阶段的异常水汽输送模式密切相关。