近20年来福州城市热环境变化遥感分析

城市热环境是城市微气候的重要组成部分,已成为近年来的研究热点。受制于卫星传感器较低的热红外波段空间分辨率,此类数据反演得到的地表温度难以反映城市热环境的实际情况。为解决这一困境,本文利用空间降尺度HUTS算法反演得到30 m空间分辨率的福州市中心城区1994年5月12日、2003年5月29日和2016年7月27日3个时相的地表温度影像。在此基础上,结合土地利用等数据对热环境的时空变化做定量分析,并进一步引入景观指数,分析近20年间福州市中心城区高温度等级斑块的形态变化。结果表明：① 近20年间随着城市拓展,福州市建成区的高温区域面积从35.75 km²增加到184.11 km²,高温度等级斑块不断从市中心向四周扩散;② 市中心的特高温斑块和高温斑块趋向破裂、分散,聚集程度下降,次高温斑块的面积与占比均大幅提升,成为建成区内高温区域的主要组成部分;③ 城市热岛比例指数URI由0.39上升到0.52,热岛效应明显加强。总体上,近20 a间福州市建成区的热环境变化较大,其中鼓楼区南部、台江区和晋安区南部的高温区域聚集现象有所改善,而仓山区、马尾区和闽侯县的大部分区域在经历快速城市化过程后温度等级明显升高。

Remote Sensing Analysis of Changes of Urban Thermal Environment of Fuzhou City in China in the Past 20 Years

Urbanization is taking place at an unprecedented rate around the world, particularly in China in the latest two decades. The effects of the intensive land-use / land-cover changes on urban surface temperatures and the consequences of these changes to human health are becoming progressively larger problems. Fuzhou, which is the capital city of Fujian province, is located in the coastal area of southeastern China. It has experienced a significant change of urban thermal environment during this period, and was recently named as one of the “new four furnace cities” in China. To study the process of changes in the thermal environment of Fuzhou city in the past 22 years, three Landsat images acquired in the years of 1994, 2003 and 2016, respectively, were used. HUTS is a widely used thermal sharpener method, which uses Normalized Difference Vegetation Index (NDVI) and surface albedo (α) to downscale the spatial resolution of thermal infrared data. It was applied to obtain LST images of higher spatial resolution (30 m) in the study area. The three downscaled LST images were then normalized, rescaled and overlaid to produce difference images to find out the changes of the thermal environment between different dates. Furthermore, by introducing simulations of different landscape patterns, these changes were evaluated and analyzed from the perspective of landscape ecology. The research results showed that, in 1994-2016, the high temperature area was increased from 35.75 km² to 184.11 km² with the city expansion. High temperature patches were expanded from city center to suburbs. On the other hand, the area and density of the high temperature patches were remarkably declined with the urban renewal. The Urban-Heat-Island Ratio Index (URI) rose up from 0.39 to 0.52, indicating that the urban heat island effect in the study area has been enhanced. Overall, the thermal environment of main urban area in Fuzhou has changed greatly in the past 22 years. Aggregation of high temperature patches was mitigated in Gulou, Taijiang and southern Jin'an Districts. Meanwhile, the temperature increased significantly in most area of Cangshan District, Mawei District and Minhou County due to rapid urbanization.