夏季臺北都市區域土地覆蓋與地表輻射熱平衡之關係

Relationship between Land Cover and Surface Radiant Heat Balance in the Taipei Urban Area during Summer

本研究針對臺北市夏季近中午都市熱島效應，使用Landsat 5 TM影像與地面氣象站資料，根據簡化地表能量平衡指標（S-SEBI）的理論，計算地表溫度、地表與空氣溫差、氣溫、地表反射率、地表放射率、蒸發散比、淨吸收輻射、短波輻射、長波輻射、地面吸收熱、顯熱、潛熱、人造表面覆蓋率、綠覆率與藍綠覆率等數值圖，解析出地表溫度迴歸預測公式、地表與空氣溫差迴歸預測公式以及氣溫迴歸預測公式，估算出各類土地覆蓋的淨吸收輻射分配給地面吸收熱、顯熱與潛熱的比例，描繪出都市熱島效應與土地覆蓋在平面與剖面上的關係，作為政府或學術單位，擬定生態城市、都市退燒與綠建築相關政策的參考依據。本研究發現：(1)地表與空氣溫差，和地表溫度存在顯著的線性關係；(2)影響都市地表溫度或空氣溫度的主要因子中，人造表面率呈正相關，而藍綠覆率與地表蒸發散比則呈現負相關；(3)地表淨吸收輻射分配給地面吸引熱、顯熱與潛熱的比例，在土地覆蓋類別存在顯著的差異。根據研究結果，建議在都市計劃層級，擬定降低都市人造表面率與增加都市藍綠覆率的政策；建議在建築管制層級，擬定基地保水、綠化、綠屋頂、綠能屋頂、冷屋頂與冷鋪面等獎勵政策與研究計畫，鼓勵民間、企業與學術單位，共同參與生態城市與綠建築的政策。

Landsat 5 TM imagery and local meteorological data were used to digital maps of the surface temperature, air temperature, surface reflectance, surface emissivity, evaporative fraction, net radian, short wave radian, long wave radian, ground heat, sensible heat, latent heat, artificial cover ratio, green cover ratio, blue and green cover ratio, etc., based on simple-surface heat balance index theory, to analyze the relationship between urban land-cover and radiant heat balance in Taipei City. The profiles of urban surface temperature, air temperatures and relative indexes were shown to present the relationship between the urban heat island effect and land-cover. This study found three important results: (1) The surface temperature is significantly related to the difference between the surface and air temperatures; (2) Artificial cover ratio is closely related to surface and air temperatures in urban areas, and is negatively correlated with blue and green ratio and evaporative fraction; (3)There exists a significant difference between the ratios of the net radian to ground heat, sensible heat and latent heat base on the different land covers. Some suggestions such as decreasing artificial cover ratio, increasing blue and green cover ratio, enhancing evaporative fraction of land cover, and improving the surface reflectance of artificial covers, such as green roof, green-energy roof, cool roof, cool pavement etc., were recommended as means by which government could promote eco-city, cool city, and green building policies.