Inter-annual and inter-decadal variations of landfalling tropical cyclones in East Asia. part I : Time series analysis

This paper is the first of a two-part series that presents results of a comprehensive study of the variations in the annual number of landfalling tropical cyclones (ATCs) in various parts of East Asia during the period 1945-2004. The objective is to identify possible trends and cycles in such variations, from inter-annual to inter-decadal, and the possible reasons for such variations. The East Asian region is divided into three sub-regions: South (south China, Vietnam and the Philippines), Middle (east China), and North (Korean Peninsula and Japan). Variations in the annual number on various time scales in each region are examined separately. Part I reports on the results of wavelet analyses of the time series of the annual number in each region, and Part II examines the possible reasons for the cycles identified in Part I.An important finding from the time series analysis is that none of the ATC time series shows a significant linear trend, which suggests that global warming has not led to a higher frequency of landfalling tropical cyclones or typhoons in any of the regions in Asia. Instead, each time series shows large inter-annual (2-8 years) and multi-decadal (16-32 years) variations. In some periods, the annual number of ATCs varies in unison among all regions of Asia. In others, one region would have an above-normal number of landfalling events, while the other regions have below-normal numbers. In general, at multi-decadal time scales, the number of ATCs in each region correlates very well with that of the total number of tropical cyclones over the western North Pacific. © 2008 Royal Meteorological Society.