Thursday, 13 February 2003
Large-Scale Characteristics Associated with Spring Heavy Rain Events over Taiwan in the Warm and Non-warm Episodes
Daily rainfall data at 15 stations in Taiwan and the gridded dataset of the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) during the period of February-March 1951-2000 were used to reveal the characteristics of large-scale circulations associated with spring heavy rain event over Taiwan in the warm and non-warm episodes. The effect of interdecadal variation on the relationship of spring rainfall and ENSO was also examined. Results showed that the different regime of interdecadal variation occurred in late-1970s exerts significant effect on the relationship between ENSO and spring rainfall in Taiwan. The pronounced positive correlation with statistical significance between cold season Nino 3 SST and the following spring rainfall over western Taiwan was only found since the late°V1970s. Large-scale environmental conditions associated with the heavy rain events for warm and non-warm episode were found to be quite different. The intrusion of a weak mid-latitude frontal system into the eastern China coastal area coupled with an anomalous anticyclone over the Philippine Sea (PSAC) in the lower troposphere was primarily responsible for the spring heavy rain event during the warm episode. While for the non-warm episode, the intrusion of a much more intense mid-latitude frontal system into China and coastal area was necessary to generate spring heavy rain event. This difference is also instrumental for more frequent occurrence of heavy rainfall events and more rainfall amount observed in the warm episode.