Spring Heavy Rain Events in Taiwan during Warm Episodes and the Associated Large-Scale Conditions

Abstract

Daily rainfall data at 15 stations of the Taiwan Central Weather Bureau (CWB) and the gridded dataset of the National Centers for Environmental Prediction?National Center for Atmospheric Research (NCEP?NCAR) reanalysis during the period of February?April 1951?2000 were used to reveal the characteristics of temporal and spatial variations of spring rainfall over Taiwan in relation to the sea surface temperature (SST) over the Niño-3 (5°S?5°N, 90°?150°W) area. Extremely heavy rain events during a warm episode were selected to study the characteristics of the associated large-scale circulations. Results showed that the spring rainfall in Taiwan was positively correlated to the Niño-3 SST not only for the overall rainfall events but also for the heavy rain events. Extremely heavy rain events occurred significantly more frequently during warm episodes as compared to those occurring during cold and normal episodes. A varimax-rotated empirical orthogonal function (REOF) analysis revealed the existence of two spatial modes, with one over northern Taiwan and the other over southern Taiwan. It was found that the intrusion of the midlatitude frontal system into the eastern China coastal area coupled with the mean state of the Pacific?East Asian teleconnection pattern was primarily responsible for the extremely heavy rain events during springtime warm episodes.