West North Pacific typhoon track patterns and their potential connection to Tibetan Plateau snow cover

Abstract

The spatial characteristics and temporal variability of the West North Pacific (WNP) typhoon tracks are studied by analyzing the spatial pattern and temporal variability of the empirical orthogonal functions (EOFs) of the WNP typhoon track density function (TTDF) from 1945 to 2004. The results show that WNP typhoon tracks exhibit three principal EOF Modes. The first EOF Mode represents the contrasting “active” versus “inactive” typhoons defined by the overall frequency and life span of the typhoons that develop in the WNP basin. The second EOF shows a north–south dipole Mode in the TTDF depicting a seesaw pattern in typhoon frequency between Northeast Asia and Southeast Asia. The third EOF describes an east–west dipole Mode in TTDF depicting a zonal seesaw pattern between typhoons that tend to make landfalls in East Asia and typhoons that tend to stay away from the East Asia landmasses. Further analysis of the EOF time series of the WNP TTDF indicates that an important climatic factor associated with the WNP typhoon activity is the snow cover over the Tibetan Plateau (TP), which is also correlated with the East Asia summer monsoon (EASM). Thus, a mechanism linking the TP snow cover and the WNP typhoon activity is the response of the EASM in the WNP region to the TP snow cover, and the subsequent effect of EASM on the development and steering of the WNP typhoons.