Skillful prediction of western North Pacific (WNP) subtropical high (WNPSH) is of utmost importance to seasonal forecast and future projection of Asian-Pacific climate. Here we show that the interannual variation of the summertime WNPSH during 1979-2009 faithfully represents the strength of East Asian summer monsoon (r=–0.92), the total tropical storm days over the subtropical WNP (r=–0.81), and the total number of tropical storms affecting East Asian coast (r=–0.76). We demonstrate that WNPSH fluctuation is primarily controlled by 1) the sea surface temperature anomaly (SSTA) in the equatorial central Pacific, and 2) the positive thermodynamic feedback between the WNPSH and a dipolar SSTA (warm North Indian Ocean and cold WNP). Based on these two mechanisms, a conceptual model can surprisingly capture about 88% of the WNPSH intensity change, and a physically-based empirical prediction model achieves comparable performance with those of the state-of-the-art coupled global climate models in re-forecasting the strength of the WNPSH. The results have profound ramification for understanding the atmospheric subtropical dynamics and predictability of East Asian summer monsoon rainfall and WNP tropical storm activity. The results indicate that monsoon-ocean positive feedback is a new source of monsoon climate predictability.

 

 

地表过程与资源生态国家重点实验室

全球变化与地球系统科学研究院