1990s末南海夏季降水与海温关系年代际转变的特征及其成因分析

The air-sea interaction over South China Sea (SCS) plays an important role in western north Pacific-East Asian climate change. Previous researches paid most attentions on intraseasonal and interannual variability of SCS air-sea interaction. This study focuses on the interdecadal change of the relationship between precipitation and sea surface temperature (SST) over SCS. The air-sea interaction processes over SCS are investigated when precipitation-SST relationship is positive and negative, respectively. The interdecadal change of precipitation-SST relationship over SCS around late 1990s is the key research. Based on observational statistic analysis, evaluation of CMIP5 models and experiments with global couple model, the influences of remote factors, such as north Pacific SST and tropical central-eastern Pacific SST et al., on atmosphere and ocean circulations over SCS are compared with the impact of local factors before and after late 1990s. The relative contribution among ocean thermal-dynamic, wind-evaporation effect and cloud-radiation effect on SCS SST tendency before and after late 1990s. This research is favorable for further understanding of the interdecadal change of SCS air-sea interaction and improving simulation and forecast of climate change over SCS. It also benefits to explore SCS climate effect.

南海海气相互作用对西北太平洋-东亚气候变化影响重大，已有研究集中探讨南海海气相互作用的季节内和年际时间尺度的变化，本项目拟从南海夏季降水与海温关系的年代际变化出发，分别研究南海夏季降水与海温正相关和负相关变化时的海气相互作用过程，重点揭示南海夏季降水与海温的关系在1990s末发生转变的物理成因。基于观测资料统计诊断分析、CMIP5模式评估和数值模式模拟，揭示1990s末前后局地因子和遥强迫因子（例如北太平洋海温、热带中太平洋海温等）对南海大气环流和海洋环境影响的相对重要性；厘清1990s末前后海洋热动力过程、风-蒸发反馈和云-辐射反馈过程等对南海海温变化的相对贡献。通过这些研究，加深对南海海气相互作用年代际转变的认识，有助于提高南海夏季气候变化的模拟与预测，而且对南海气候效应的研究具有重要意义。

南海海气相互作用对西北太平洋-东亚气候变化影响重大，已有研究集中探讨南海海气相互作用的季节内和年际时间尺度的变化，本项目着重从南海夏季降水与海温关系的年代际变化出发，基于观测资料统计诊断分析和数值模式模拟，揭示了1990s末前后PDO位相转变，其调整前冬到夏季赤道中东太平洋海温的衰减过程，从而使得影响南海大气环流和海洋环境的主要遥强迫因子由热带印度洋海温向赤道东太平洋海温转变，热带印度洋海盆一致增暖模态对南海-西北太平洋异常反气旋环流的作用明显强于赤道东太平洋冷海温，进而在1990s末之后南海西南部海温的局地强迫作用凸显。1990s末前后南海东北部主要是大气强迫海洋过程，云辐射过程占主导；而南海西南部在1990s末之前以大气强迫海洋过程为主，海洋动力过程大于净热量通量的贡献，在1990s末之后南海西南部以海洋强迫大气为主，云-辐射反馈效应抑制局地海温的增暖。这些成果丰富了对南海海气相互作用年代际转变的认识，有助于提高南海夏季气候变化的模拟与预测，而且对南海气候效应的研究具有重要意义。