全球暖化影響之下日降水與極端降水事件變化之探討

Abstract

Weather and climate events can have serious and damaging effects on human society (such as flood, heavy precipitation, heat wave, etc.). In this study, the simulation of the variability and extremes of daily rainfall for the present and the future climate is investigated. This is done by the ECHAM4/OPYC3 GSDIO for the period 1960-1990 and the Special Report on Emission Scenarios (SRES) A2 (rapid CO2 increase) and B2 (moderate CO2 increase) forcing scenario for the period of 2070-2100. Moreover, observational rainfall data from the Global Precipitation Climatology Project (GPCP, 1996-2004) is considered. In general, analysis of model data revealed agreement with observations. For the future, the ECHAM4/OPYC3 simulates the variability of the daily rainfall predicts the most pronounced precipitation changes are found in high latitudes of the Northern Hemisphere for the winter. However for some continental areas, the change of mean precipitation and rainfall intensity is not coincident. A clear reduction in the probability of wet day, in particular, for the large areas in the northern mid-latitudes and subtropics. Despite this decrease the relative contribution of heavy precipitation has grown due to the corresponding increase of the scale parameter of the gamma distribution. This implies a more extreme climate with higher probabilities of droughts and heavy precipitation events. Furthermore, the variability of the 99.7th percentile also implies in the area of heavy precipitation, stronger heavy rainfall will happen in the future, vice versa. Extreme value theory based on GEV and GPD provides a much more complete analysis of the statistical distribution of extreme rainfall event. We have obtained statistically significant spatial models of the three parameters of GEV and GPD. N-years return level form GEV or GPD all show the relative changes in extreme precipitation is larger than change in total precipitation.