基于卫星遥感的长江三角洲地表热环境人口暴露空间特征

研究城市地表热环境变化的时空演变规律对防灾减灾具有重要意义。本研究以卫星遥感的夜间灯光,植被指数,高程和坡度为自变量构建了适用于人口空间分布估算的随机森林模型,结合卫星遥感反演的地表温度数据,以2016年夏季为例,研究了1km分辨率的长江三角洲地区夏季地表热环境人口暴露分布特征。研究表明:(1)利用随机模型对长江三角洲2016年人口进行1000m格网空间化分布模拟,变量解释度达到80%,人口空间化结果接近实际。(2)人口密度高值区和夏季大部分月份内的地表热环境高温区和人口暴露高和极高风险区总体有较好的对应。6月皖北地区高温区面积增大导致地表热环境的人口暴露风险较高等级的面积比例高于其他月份。(3)在月和季节平均尺度上,地表高温热环境暴露极高和高风险区域面积极少,处于沿海地区、长江下游沿线以及各县区的中心城市;中等暴露风险区域主要分布在东部及中心城市周边地区;低暴露风险区分布在东北部内陆地区和东北部人口数量相对较少地区。

Population Exposure Risk to Land Surface Thermal Environment over Yangtze River Delta Based on Multi-Satellite Data

Under the background of global warming and rapid urbanization, the urban heat island effect is the most obvious feature of urban thermal environment, so it is of great significance to study the temporal and spatial evolution of urban thermal environment change for disaster prevention and mitigation. In this study, we use the random forest model to estimate the spatial distribution of population in the Yangtze River Delta by taking the latest generation of night light satellite NPP/VIIRS data, the normalized vegetation index, the digital elevation model and topographic slope data as independent variables. Then we combine the surface temperature data retrieved by MODIS satellite remote sensing, taking the summer of 2016 as an example, to study the risk of surface thermal environment exposure and its special distribution in the Yangtze River Delta at 1 km resolution. The results show: (1) The explanatory degree of 1000 m grid spatialization variables for the population of the Yangtze River Delta in 2016 is 81.61% by using the random forest model. The simulated population can truly reflect the regional difference of population distribution in the Yangtze River Delta, closer to those of actual population. (2) The high value area of population density has a good correspondence with the high temperature areas in the surface, the high populaton exposure areas and the high risk areas exposed in most months of the summer, while in June, the area of high temperature zone in the northwestern part of the Yangtze River Delta increased, which is asymmetrical to the area of high density population, and thus the exposure risks of surface temperature from low to high levels are higher than those in other months. (3) On monthly and seasonal scales, the high risks for population exposure to the land surface thermal environment are mainly located in the coastal areas, along the lower reaches of the Yangtze River and in the central urban areas of the counties. The middle risks for population exposure to LST is mainly distributed in the surrounding areas of the eastern and central cities; the low exposure risk areas are distributed in the inland areas of the northeast and the relatively small population areas of the northeast Yangtze River Delta.