Contribution of Tropical Cyclones to the Seasonal Change Patterns of Precipitation in the Western North Pacific: Estimation Based on JRA-25/JCDAS

Abstract

The contribution of tropical cyclones (TCs) to the seasonal change patterns of precipitation in the western North Pacific was studied using Japanese long-term reanalysis/JMA Climate Data Assimilation System (JRA-25/JCDAS) data from 1979 to 2006. The seasonal change patterns are based on the three types of Hattori et al. (2005) classified by a northward shift and increase in precipitation from June to August. We show that the contribution ratio of TC precipitation in the western North Pacific, on average and maximum being 19.8% and 46.7%, becomes larger as monthly mean total precipitation increases. Among the three types of seasonal change pattern, TC precipitation varies corresponding to the features of total precipitation and contributes 0.5-1.8 mm day-1 variation of the regional mean precipitation. Between the two types which show a northward shift and an increase in precipitation, TC causes 31%-41% of the total precipitation difference. TC precipitation highly contributes to the type that shows the largest northward shift and precipitation increase; its maximum ratio reaches 70% east of Taiwan and TCs contribute 3-5 degrees of the northward shift of the precipitation area in the western North Pacific.