基于气候复杂网络的中国东部极端降水与夏季雨带分布研究

Summer precipitation belt identification and classification in Eastern China is one of the key scientific problems for summer monsoon dynamics, which have come to an agreement that precipitation belt is mainly influenced by the seasonal precipitation. In recent years, abservation example show that extreme precipitation has more and more influence on summer precipitation belt in East China, especially extreme precipitation events in Jun. 2011, which directly form the mainly precipitation belt in that summer. So influence of extreme precipitation on summer precipitation belt in East China has become a new important problem in climate research.However, few attentions have been paid to the belt identification and the classification of the summer extreme precipitation in Eastern China, and also to correlation between the change of SST of West pacific warm pool and the seasonal extreme precipitation pattern, so urgent need to carry out relevant studies. This research study the similar dynamics behaviors of summer extreme precipitation in Eastern China based on the climate complex network theory, in order to identify the extreme precipitation belt, reveal the main modes of extreme precipitation pattern and corresponding changes. Then showing the probable influence on trditinal precipitation belt in summer. Based on these research, change of former winter SST of West pacific warm pool which might have good influence on the main modes of extreme precipitation pattern is also analyzed, in order to reveal the corresponding correlations between the SST of West pacific warm pool and the main modes of extreme precipitation pattern, and probable changes under the global warming, with the similarly generalized equilibrium feedback analysis method. This might be also helpful to the research of spatial distribution of summer precipitation in East China.

中国东部夏季雨带分布的年际变化始终是季风气候动力学研究的重要科学问题，目前已对由季节降水的距平确定雨型达成共识。近几年，尤其是2011年6月的极端强降水事件的频发导致了当年初夏长江下游地区久旱急转为大暴雨集中期，从而成为当年夏季的主要雨带。全球增暖背景下，极端强降水对我国夏季雨带位置产生重大影响，已成为新的热点问题。因此，需要进一步研究极端降水的强度和频次等是否具有一定的雨型特征，对夏季雨带的分布有何影响。本项利用气候复杂网络理论，分析中国东部夏季站点极端降水事件动力学统计特征的空间相似规律，客观识别极端降水事件的区域特征；根据夏季极端降水事件的累积量，给出季节尺度极端降水的雨型主模态和时间变化系数，并与夏季总降水量的空间分布进行对比分析，揭示极端强降水对夏季雨型的贡献；在此基础上，着重分析前冬西太平洋暖池海温影响夏季极端降水雨型的机制，为中国东部夏季降水雨带的分布研究进一步提供科学依据。

本项目揭示了全球变暖背景下中国夏季极端降水空间分布和时间演化具有新的特征。主要总结为，首先，采用统计方法揭示了1980年代前，100°E以西地区的中国夏季极端降水对总降水的贡献率为16-20%，以东地区则达到20%以上，部分地区达30%左右；转折后，中国东部大部分地区夏季极端降水贡献率则均有所增长，且EOF展开的主要模态发生一定程度的调整。其次，基于复杂网络理论，构建了东亚夏季极端降水的复杂网络，结合结构特征量将东亚地区夏季极端降水分为（1）内陆非典型性季风极端降水区和（2）南部典型性季风极端降水区。构建了极端降水的非线性预测模型，验证了该方法在东亚夏季极端降水预测中的潜在应用价值。第三，探讨了持续性强降水与长江中下游流域夏季降水时-空分布之间的关系，从持续时间、控制面积和降水贡献率三个方面讨论持续性强降水对夏季总降水量的贡献，结合EOF分析将长江中下游流域夏季持续性强降水的空间范围划分为四种空间型，并给出与中国东部夏季降水的可能联系。第四、揭示了东亚夏季降水在20世纪90年代末发生了年代际转折，并开展动力模式预测的订正研究。订正后，BCC_CGCM中表现为30°N-50°N范围的东亚夏季降水纬度-时间剖面图的ACC由原来的-0.01改进为0.18；BCC_ CSM中则表现为ACC由-0.09改进为0.02，有效改进了模式中蕴含的关于1990s末东亚夏季降水年代际变化信息。