The significant influence of the precipitation anomalies in the tropical western North Pacific (WNP) on the rainfall and circulation anomalies in East Asia has been well demonstrated by previous results. However, most of these results are obtained via linear approaches (correlation or regression) or composite differences, assuming that the relationship between circulation and precipitation anomalies is basically linear. 

In this study, Prof. LU Riyu et al. from the Institute of Atmospheric Physics revealed an asymmetry in this relationship: positive precipitation anomalies over the WNP, in comparison with their negative counterparts, are more closely related to rainfall anomalies along the East Asian rain belt and the meridional circulation pattern. 

Figure. Composite precipitation anomalies for (a) positive and (b) negative WNPRI cases. Shading indicates regions of significance at the 0.05 level. The zero contours are omitted, and the contour intervals are 0.5 mm d^？1. (Figure plotted by IAP)  

The results in this study indicate an asymmetric tropical–extratropical relationship over the WNP and East Asia, i.e., enhanced WNP rainfall corresponds to stronger extratropical anomalies, while suppressed WNP rainfall corresponds to weaker extratropical anomalies. This asymmetric relationship makes the investigation on this tropical-extratropical interaction facing new challenges. 

Reference 

Ri-Yu Lu, Xiao-Wei Hong,  Xin-Yu Li, Asymmetric association of rainfall and atmospheric circulation over East Asia with anomalous rainfall in the tropical western North Pacific in summer, Atmospheric and Oceanic Science Letters, 9(3), doi: 10.1080/16742834.2016.1161489. 

Download: http://www.tandfonline.com/doi/full/10.1080/16742834.2016.1161489 

Contact: LU Riyu, lr@mail.iap.ac.cn