A climatological study of tropical cyclone rainfall in Vietnam

Abstract This study investigated the characteristics of the rainfall as-sociated with tropical cyclones (TCs), using the TC best-track data and daily rainfall data from 15 meteorological stations for the period 1961−2008 for the coastal region of Vietnam. In ad-dition to investigating the TC rainfall amount, we estimated the TC rain ratio and the ratio of TC heavy rainfall days (TC_R50) and interpreted these parameters for El Nino and La Nina years. Our results show that the maximum TC rainfall occurs from July to September in the northern region, whereas the total rainfall at southern stations is mainly composed of non-TC rainfall. The TC rainfall amount is concentrated in the central region, with a peak in October-November. The TC rain ratio varies from 0 to ~25%, showing a maximum value in the region of 16°N−18°N in September. The mid-central region of Vietnam has maximum TC_R50 ratio in September-October corresponding to its highest TC frequency in the same period. During El Nino (La Nina) years, the TC rain ratio and TC_R50 ratio in the central region show a significant decrease (increase) in October-November. The La Nina phases more strongly affect TC rainfall than the El Nino phases, particularly in central Vietnam.