都市熱島效應及城鄉降雨型態差異之調查研究 Investigations on urban heat island effects and the difference of rainfall types between metropolitan and country areas.

受全球暖化現象的影響，近年來世界各地極端氣候出現的頻率明顯地增加；台灣地區亦受其影響，除降雨強度及分布顯著改變外，大氣溫度亦出現極端的紀錄，此一現象尤以都會區為甚。都會地區的高溫除受暖化影響外，都會區的熱島效應亦為助漲溫度攀升不降的原因之一。台灣地區都市程度相當高，已有研究顯示台北等市區的地表面溫度高於鄰近鄉村地區的樹林水田達5℃，尤以晚間氣溫的差異更大。另一方面，都市熱島效應所引發的午後熱對流改變自然的大氣環流，對都會區的降雨型態亦會有所影響。基於此，本計畫擬探討都會公園綠地對降低氣溫的效應，並比較台灣地區城市與週遭鄉野氣溫及降雨型態的差異。本計畫已於台北植物園的綠地及辦公大樓樓頂架設溫溼度風速、風向觀測塔，監測該等氣象因子，並比較其間的差異，以探討綠覆蓋對降低氣溫的功效；從6個月的紀錄顯示，樹冠層頂、林下及建築物頂樓的平均溫度分別為：26.15、24.80與28.04℃。分析蓮華池研究中心氣象站降雨強度紀錄，顯示該地區降雨多屬延時3~6小時，在1990年前之降雨多屬前鋒型降雨，而1990年後之降雨則多屬中鋒型。
The occurrence of extreme climate has been significantly increased in the last decades due to the effects of global warming. Taiwan is also affected by the effects of global warming and shown the changes of rainfall intensity and distribution and has frequently occurred extreme temperatures especially in the metropolitan areas. The higher temperatures in the metropolitan areas are also believed to be increased due to the urban heat island effects. The city dome effect caused by heat stored in buildings and road surface, thermal emission from air conditioning equipment, and the reduced plant cover is thought to cause the heat island phenomenon and increasing green coverage is considered the most cost-effective method to reduce temperatures in urban areas. The degree of urbanization in Taiwan is relative high and there are reports indicated that the surface temperatures in Taipei and other cities of Taiwan was higher than that in the woody and paddy fields of nearby rural areas up to 5 ℃, and the differences were particularly greater at nighttime. On the other hand, the changes of natural thermal convention and atmospheric circulation in the summer afternoon of metropolitan areas caused by urban heat island effects will have an impact on rainfall patterns and rainfall durations. Therefore, this project will investigate the effects of green coverage in reducing temperatures and compare the difference of rainfall patterns between city and the surrounding countryside. This project has established observation towers at Taipei Botanical Garden and administrative building of TFRI to monitor meteorological factors such as: air temperature and humidity wind speed, wind direction and compared the differences between them in order to explore the effects of green coverage in reducing temperatures. From the 6 months’ monitored data showed that the average temperature of top canopy, under canopy and top building were 26.15, 24.80 and 28.04℃, respectively, and has significant difference. Historical records of rainfall of the Lienhuachih metrological station were also analyzed to investigate the difference of rainfall distribution between metropolitan area and countryside areas for exploring the impact of urban heat island effects on rainfall patterns. The primer results showed that the rainfall durations for that area were most between 3 to 6 hours and the rainfall pattern before 1900 was mostly classified as front peak and that after 1900 was mostly classified as middle peak.