The study of the urban thermal environment and thermal effect is one of the most important topics in city climate and environment research. Because of global climate change and urbanization, extreme high-temperature events have occurred frequently in recent years and have greatly impacted the daily lives and social activities of people. Therefore, it is necessary to analyze the spatiotemporal change of land surface temperature (LST) and the response of urbanization to the urban thermal environment. The aforementioned type of study is significant for improving the city thermal environment, and reducing the frequency of extreme high-temperature events.
This work has the metropolitan city of Beijing as its study area. As a major city in the world, Beijing has been facing many environmental problems, for example, atmospheric pollution, water pollution, meteorological disasters, and others. Extreme high-temperature events are one of the most common meteorological disasters in the city. In the present study, we integrated theories of remote-sensing quantitative inversion methods, GIS spatial analysis methods, and geostatistics technology in our research on thermal environment issues. We analyzed the response of urbanization to the urban thermal environment of Beijing. First, the MODIS LST data for extreme high-temperature events in 2000 and 2010 were used to analyze the distribution and evolution of surface temperature in the city. Variability and isothermal variation analyses were used to study the distribution of thermal environment. In addition, Defense Meteorological Satellite System (DMSP) Operational Linescan System (OLS) data from 2000 and 2010 were selected to analyze the expansion of urban area in Beijing from 2000 to 2010, using profile analysis and grid calculation. Finally, the response of LST to urbanization was investigated, based on qualitative and quantitative analysis using a combination of the LST and DMSP/OLS data.
Two main conclusions were drawn, as follows: (1) The LST at the time of extreme high-temperature events increased significantly during 2000-2010. The magnitude of LST increase varied spatially, with that of the city function expansion and city development zones greater than that of the capital function core and ecological conservation development zones; (2) expansion of the Beijing urban area was obvious over the last decade, with the Forbidden City as the center. The spatial distribution of the surface temperature increase was very consistent with the city development space. The average night light index increased, as did the average change of surface temperature. From the present study, we draw the conclusion that the urbanization had a great impact on the LST distribution, which increased with development of the city. This work can provide useful information for urban planning and urban living environment improvements.
There are some inadequacies that require further study. First, we only selected LST data during daytime. Nighttime LST data should be considered in the future. Second, the distribution of LST was influenced not only by the urbanization, but by natural causes. An analysis relating the urban thermal environment and natural causes would advance understanding of the mechanism of the urban thermal environment. These inadequacies will be resolved in the next step of the study.