Abstract
In this study, we analyzed the impacts of Western North Pacific Subtropical High (WNPSH) on tropical cyclone (TC) activity on both interannual and interdecadal timescales. Based on a clustering analysis method, we grouped TCs in the Western North Pacific into three clusters according to their track patterns. We mainly focus on Cluster 1 (C1) TCs in this work, which is characterized by forming north of 15° N and moving northward. On interannual timescale, the number of C1 TCs is influenced by the intensity variability of the WNPSH, which is represented by the first Empirical Orthogonal Function (EOF) of 850 hPa geopotential height of the region. The WNPSH itself is modulated by the El Niño–Southern Oscillation at its peak phase in the previous winter, as well as Indian and Atlantic Ocean sea surface temperature anomalies in following seasons. The second EOF mode shows the interdecadal change of WNPSH intensity. The interdecadal variability of WNPSH intensity related to the Pacific climate regime shift could cause anomalies of the steering flow, and lead to the longitudinal shift of C1 TC track. Negative phases of interdecadal Pacific oscillation are associated with easterly anomaly of steering flow, westward shift of C1 TC track, and large TC impact on the East Asia coastal area.
Highlights
Tropical cyclones (TCs) over the western North Pacific (WNP) can be highly destructive, resulting in devastating losses of human life and property in coastal regions of East Asia
The Cluster 1 (C1) TCs mostly formed over the WNP north of 15° N, under the influence of the Western North Pacific Subtropical High (WNPSH) and moves northward in general, the black line in Fig. 1a representing the average movements of C1 TCs
We focused on the mechanism responsible for the interannual and interdecadal variability of C1 TCs
Summary
Tropical cyclones (TCs) over the western North Pacific (WNP) can be highly destructive, resulting in devastating losses of human life and property in coastal regions of East Asia. TCs tend to form over the southeastern WNP with stronger intensity during the warm phases of ENSO (Chan 1985, 2000; Wang and Chan 2002; Camargo and Sobel 2005; Han et al 2016; Patricola et al 2018; Zhao and Wang 2019) Other factors such as the sea surface temperature anomalies (SSTAs) in the Indian Ocean (IO) and the tropical North Atlantic (TNA) can modulate the interannual variability of WNP TC activity (Zhan et al 2011a, 2014; Tao et al 2012; Cao et al 2016; Yu et al 2016)
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