热带海温与青藏高原热力强迫协同变化对亚洲夏季风爆发的影响研究

The Asian summer monsoon (ASM) onset is featured by the vertical coupling between the upper- and lower-level circulations and the formation of monsoon convection. The ASM onset exhibits prominent transient characteristic compared with the evolution of monsoon circulation in boreal summer, acting as a precursor for the beginning of the Chinese summer rainy season. The changes of the sea surface temperature (SST) in tropical ocean and the Tibetan Plateau (TP) thermal forcing from winter to summer show great seasonal phase-locking, and they have been treated as the two important factors for the ASM onset. The distinct interannual variation of these two factors can increase the uncertainty of the seasonal prediction on the ASM onset time based on the sole factor. Thus, this proposal will start with the research on the association between the formation of TP atmospheric heating source and the tropical SST via the theory analysis, data diagnosis and numerical experiments. And we tend to emphasize (1) the relative contribution of tropical SST anomalies and TP heating source to the transient variation of monsoon circulation during the ASM onset, and to further discuss (2) the collaboration of tropical SST anomalies and the TP heating source on the early or late onset of ASM, as well as the associated critical physical process. Our purpose is to reveal the influence of land-air-sea interaction on the interannual variability of ASM onset and its mechanism, and further to develop a theory for the multi-factors-based quantitative prediction of the ASM onset time.

亚洲夏季风的爆发表现为季风区高、低层环流的垂直耦合和季风对流的建立，是中国汛期降水开始的前兆信号。与盛夏季风环流的演变过程相比，夏季风爆发具有明显的瞬变特征。由冬到夏热带海温（SST）与青藏高原热力强迫的演变具有明显的季节锁相特征，是影响亚洲夏季风爆发的两个关键因子，但两者季节变化的年际差异却十分显著，所以基于单因子预测亚洲夏季风爆发时间存在较大不确定性。为此，本项目拟采用理论分析、资料诊断和数值模拟相结合的技术路线，以青藏高原热源的建立及其与热带SST之间的联系为切入点，重点讨论在季节转换过程中（1）两个关键因子对亚洲夏季风爆发期间环流系统的相对贡献及其瞬变过程；（2）年际尺度上两个关键因子之间的协同变化对亚洲夏季风爆发时间的影响及其物理机制。基于上述研究，试图揭示海-陆-气三者联动对亚洲夏季风爆发年际变率的影响过程和机理，提出基于“多因子”的亚洲夏季风爆发时间的定量预测理论。