中国城市扩展对气温观测的影响及其高估程度

由于中国城市扩展导致部分气象站点被动进入城市内部,从而造成对区域气温的高估.本文利用遥感多期影像对中国700多个气象站点各历史时期的下垫面进行判别,得到"进城"站点及其进城时间.通过比较"进城"站点的观测数据和背景气温,计算出70年代以来"进城"气象站点上的平均热岛效应强度,并对热岛效应强度的季节性筹异进行了分析,得出70年代以来秋冬季节的热岛强度高于春季和夏季的结沦.通过比较真实气温和背景气温的空间数据,识别出了气温高估区域,得出中国东部地区的气温高估略高于中部地区,东部地区和中部地区的气温高估均远高于西部地区的结论.通过计算真实气温和背景气温序列的年平均气温变化趋势,得出近40年来全国的增温值约为1.58℃,其中凶城市扩展带来的增温贡献约为0.01℃,在气温高估的核心区域的贡献约为0.09℃.

Impact of Urban Expansion on Meteorological Observation Data and Overestimation to Regional Air Temperature in China

Since the 1970s, some meteorological observation stations in China 'entered' into cities passively due to urban expansion. The changes in underlying surface and building environment around the stations have had influences on the observation of air temperature, leading to overestimation on the regional air temperature. In this study, the surface underlying 756 meteorological stations across China was firstly identified based on the MSS images of the 1970s, TM images fore-and-aft 1990, and ETM images fore-and-aft 2000 and 2005, to distinguish the stations that 'entered' into cities. Then, after removing the observed data at these stations influenced by urban expansion, we built a dataset of background air temperature by interpolating the observed data at all the left stations. The average Urban Heat-island Intensity (HI) since 1970 was estimated by comparing the two datasets. The results show that overestimation on regional air temperature does occur due to urban expansion, with higher HI in autumn and winter than in spring and summer. Spatially, the overestimation is relatively higher in eastern China than in the middle part of China, however it is much higher in the above two regions than in western China. In the last 40 years the average temperature in China increased by about 1.58 ℃, among which about 0.09 ℃ was attributed to urban expansion in some regions.