Contribution of Tropical Cyclones to Rainfall in the Philippines

Abstract

AbstractTropical cyclone (TC)-induced rainfall (TC rain) in the Philippines was investigated using a combination of ground and satellite observations to produce a blended 64-yr precipitation dataset. A total of 1673 TCs were examined using best track data from the Japan Meteorological Agency. Rainfall from 100 (~1110 km) of the TC center was considered as TC-induced rainfall. TC rain contribution is highest in the northern Philippines, particularly along the western coast of Luzon (up to 54%), and lowest in the southern islands of Mindanao (6%). The high TC rain contribution is attributed to the enhancement of the Asian southwest monsoon by TCs located to the northeast of the Philippines. An unsupervised clustering method, k-means clustering, was used to divide the archipelago into four climate subtypes according to monthly rainfall variation. Interannual variability of rainfall from climate clusters with high TC rain contribution generally follows the variability of TC rain. On the other hand, the variability of low TC rain clusters is mainly influenced by El Niño–Southern Oscillation (ENSO). All clusters show increasing trends of 16.9%–19.3% decade−1 in TC rain percentage contribution since 2000. This study hypothesizes that this increasing trend is due to changes in the characteristics of TC steering mechanisms and thermodynamic properties east of the Philippines in the past one and a half decades.