TRMM、CMORPH、PERSIANN三組衛星資料對臺灣降雨日變化特色的表現能力評估

Abstract

本研究檢驗TRMM、CMORPH及PERSIANN三組衛星觀測降雨資料對於臺灣降雨日變化特色的表現能力。檢驗過程從降雨日平均值(daily mean)及日變化量(diurnal variation)兩方面進行探討。在降雨日平均值方面，本研究發現雖然三組衛星產品皆有低估實際降雨量的缺點，但三者皆能大致掌握到「日平均降雨最大值區域，隨季節變化有逆時針移動」之特性，且三者之中以TRMM的表現最好。在降雨日變化量方面，本研究發現TRMM亦較CMORPH及PERSIANN更能掌握臺灣春、夏、秋三季降雨之日變化時、空分布，即呈現最大降雨發生時間及區域為午後山區。但在冬季降雨日變化量方面，三組衛星產品則皆無法良好地表現出「臺灣東邊夜間降雨，西邊清晨降雨」的區域差異特色。最後，本研究亦針對春、夏、秋三季，探討TRMM對於臺灣日變化降雨的掌握度比COMRPH及PERSIANN兩組衛星資料好的可能原因。結果發現，三組衛星資料對於臺灣地區降雨差異的表現，主要來自於衛星資料對陸面降雨、地形降雨的表現能力差異。相較之下，三組衛星資料對臺灣鄰近海面移動系統的降雨表現差異則較小。This study evaluates the performance of TRMM, CMORPH, and PERSIANN precipitation productions in representing the characteristics of diurnal precipitation (including daily mean and diurnal variation) in Taiwan at four different seasons: spring (March to May), summer (June to August), autumn (September to November) and winter (December to next February). Results show that TRMM is the best among the three for depicting both the spatial-temporal characteristics of daily mean and the diurnal variation of precipitation in Taiwan at the seasons of spring, summer and autumn. While for the winter season, none of the three satellite products can capture the observed regional difference in the timing of occurrence of maximum diurnal precipitation. Possible cause for the differences among TRMM, CMORPH and PERSIANN in depicting the characteristics of diurnal variation of precipitation in Taiwan at the seasons of spring, summer and autumn is also discussed. Analyses also show that the three satellites have larger differences in depicting the diurnal variation of precipitation in Taiwan, as compared to the differences in depicting the diurnal variation of precipitation over the nearby ocean.