台南是台灣最早發展的城市，隨著人口的增長，使得城市的規模日益擴大，都市的熱島效應也因此增強。先前的研究指出雷雨所造成降雨的地區可能會受到都市熱島效應的影響而有所改變，尤其在夏季時，都市地區的高溫現象會強化地區的熱對流系統，而改變地形效應之降雨和地區。為了探討都市發展對於區域降雨之影響，本研究將分析都會區之不透水層鋪面比率(Impervious Surface Area；ISA)與熱島效應(Urban Heat Island；UHI)強度間之關係，進而探討都市熱島強度在都會區降雨型態之影響。 首先利用Landsat衛星資料提供的可見光與熱紅外波段資料分別進行各年份地物之分類與ISA值之計算，做為都市化的指標，以及地表溫度之反演與UHI強度之估算。其次則使用降雨的網格資料與再分析風場探討不同風場對於熱島效應降雨之影響。最後使用中央氣象局1993年至2012年地面測站的降雨觀測資料，分析整體降雨的趨勢與變化，並結合UHI的變化探討其間之相關性。 結果顯示，台南區與新市區之ISA分別以每年約0.012與0.016的速度增加；UHI則分別以每年約0.092℃與0.21℃的強度增溫。另外，UHI與ISA的相關性很高，尤其在新市與台南區皆大於0.8，表示都市的發展確實增強了熱島效應之強度。研究也指出在都市測站午後雷雨的降雨量有增加的趨勢，而山區測站則受都市熱島效應的影響，而相對減少，後續仍需藉由模式進行深入之探討。 ;Tainan is the oldest city in Taiwan and the increasing population density leads her to be a big city, as well as intensify the urban heat-island effect. The previous researches indicate that the precipitation could be influenced by the intense urban heat-island effect, such as the thunderstorm for example. In summertime, urban heat can generate the convection can be caused from the heat surface of urban area, and then reduce the rainfall rate from terrain lifting effect. As a result, the regional precipitation pattern could be altered, especially during the summertime. In order to have better understanding the impact of urbanization on the precipitation, impervious surface area (ISA) as the index of city urbanization associated with the intensity of urban heat island effect (UHI) are used in this study. Landsat data is utilized in this study since the visible and thermal Infrared spectral bands can be provided for calculating the data of classification and UHI at the same time. After the land cover type classification, we can derive the value of ISA around the areas of Tainan city and the changes along with the time. Then using TCCIP precipitation and ECMWF wind field data to find the precipitation distribution in different wind field. Final, the rainfall data during July and August from 1993 to 2012 which exclude the data in typhoon days from Center Weather Bureau (CWB) over Tainan city are collected to investigate rainfall trends in each station and examine the correlation between ISA and precipitation. The result indicated that high ISA and UHI value was locating in urban area. Following the urbanization, UHI increased along with the ISA during the past 17 years and there have high correlation between UHI and ISA. The result also indicate that the rainfall trends increasing in urban area and decreasing in mountain area because of Urban Heat Island obstruct the water vapor which is bring from ocean to mountain area.
