基于遥感的上海城市热岛效应与植被的关系研究

选择2001年3月和7月上海地区的陆地卫星ETM+影像，利用ETM+热红外亮温计算模式将6波段影像灰度值转换成像元亮温，由此直接表征地表温度分布，对城市亮温热岛的空间分布特征、强度变化及其相关影响因素进行了概括.通过提取归一化植被指数(NDVI)，并基于统计方法对不同下垫面类型的局域亮温和NDVI进行回归分析，一致证明亮温与植被水平呈明显负相关,且植被降低下垫面温度的效果夏季强于春季；对回归方程斜率的比较又揭示出植被对地面温度的影响受下垫面用地类型结构的制约；增加相同水平的植被，夏季白天降温程度在植被面积占优势的地区不及非植被或少植被区.建议应根据不同类型的下垫面环境进行针对性的植被规划.

Relationship between vegetation and urban heat-island effect in Shanghai

The gray-scale values of band 6 of Shanghai Landsat ETM+ images acquired on 13 March and 3 July in 2001, were converted to pixel brightness temperature to represent the land surface temperature distribution by calculating model of ETM+ TIR brightness temperature. And the overall characteristics, variability, and related influencing factors of urban brightness temperature heat island was generalized. Then regression analyses between Normalized Difference Vegetation Index (NDVI) and brightness temperature on local scale in different landcover types revealed a significant inverse correlation between radiation temperature and vegetation level, and the cooling effect of vegetation on underlaying surface was stronger in summer than in spring. Furthermore, comparisons of the regression lines’ slopes implied that the vegetation’s influence upon surface temperature is conditioned by the underlaying surface structures, so while increasing same vegetation in well-vegetated and sparsely or non-vegetated areas during the summer daytime, the former’s extent of temperature declining is inferior to the latter’s. As suggested, vegetation planning must be adaptive to the local conditions of different land environment.