An Inferential Statistical Study on the Climate Characteristics of Tropical Cyclones over the Northwestern Pacific

This chapter presents an inferential statistical study on the climate features of cyclone activities in the Northwestern Pacific (WNP) using data from 2,029 tropical cyclones (TCs) obtained within 60 years (1949–2008). The analysis shows the following results. (1) The annual genesis frequency of TC from 1949–2008 exhibits a statistically significant downward trend. The frequencies of tropical storms, typhoons, and strong typhoons have also declined, although less significantly than that of TCs. The interannual occurrence frequency of TCs has a statistically significant high value from 1960–1975, whereas its value is low from 1990–2008. (2) The highest frequency occurs at 14°–19°N and 115°–120°E within the 5° × 5° area, which is a narrow ocean surface to the west of Luzon Island in the South China Sea. (3) In general, the more southward and eastward the location of the TC genesis is, the stronger the TC is. Comparatively speaking, the effect of longitude on TC intensity is greater than that of latitude. Moreover, the interaction impact on TC intensity exists between latitude and longitude. This study provides new information that can improve the understanding of TC climate features over the WNP.