| The urbanization in China not only brings social,economic and cultural development,but also brings challenges to the urban environment.Urban construction and population gathering have important influence on the development of surface thermal environment.As an excellent data source for monitoring urban development and human activities,remote sensing nighttime light provides a new perspective for the study of urban surface thermal environment characteristics.The change of urban surface thermal environment is affected by the typical types of underlying surface with different spatial characteristics and human production activities together.Many scholars carry out the research on the change and development of urban surface thermal environment from the perspective of natural factors such as urban underlying surface,but there are few studies on the influence of human development factors related to production activities based on lighting on the spatial thermal environment.This study introduced the NTL intensity into the remote sensing analysis of the urban surface thermal environment,and constructed a spatio-temporal dynamic relationship model between light intensity and surface temperature based on light grade classification to analysis the spatio-temporal distribution and characteristics of land surface temperature directly using NTL intensity,which break through the traditional idea of using NTL to obtain intermediate products for LST studies,such as urban impervious surface area and building density,and then used the intermediate products to conduct urban thermal environment research.The study promoted the research on the surface thermal environment transforming from simple surface detection to the detection combined with the intensity of human social and economic activities.It is verified that the measurable surface nightlight intensity data can be used as a measure to depict and understand the influence of large-scale urban development and human activities on surface temperature.In this study,two kinds of noctilucent data(Defense Meteorological Satellite Program/Operational Linescan System,(DMSP/OLS);Visible Infrared Imaging Radiometer Suite/Day/Night Band,(VIIRS/DNB))commonly used in the world were selected,together with corresponding surface temperature data to construct a spatio-temporal dynamic relationship model between light intensity and surface temperature based on hierarchy.Based on the classification of light radiation intensity at low resolution and medium resolution,the temporal and spatial dynamic characteristics of surface temperature in different nighttime light levels across China are analyzed.The trend and reason of surface temperature change are analyzed by combining the characteristics of urban surface environment spatially,natural climate change and seasonal human activities temporally.In order to further analyze the changes of surface thermal environment,verify the synergistic influence of urban natural environment elements and human environment elements on urban thermal environment,further,by using medium-high resolution data and taking Beijing as the research area,the characteristics and trends of urban development indicators(NTL field)and surface environmental indicators(temperature field,greenness field,grayness field)were further analyzed on the urban scale.Through the spatial distribution characteristics and interaction of urban brightness,grayness and hotness,the characteristics of urban surface thermal environment are analyzed in detail.The results show that:(1)The method of spatial-temporal dynamic relationship model between light intensity and surface temperature based on hierarchical division proposed in this paper,realizes the organic combination of night light data and surface thermal environment data.Practical research and typical application analysis are carried out in two different scales.It is shown that night light data can provide a new perspective and direction for the study of the surface thermal environment from the detection of the surface environment to the detection combined with socio-economic parameters.(2)As for the grading of low-resolution light radiation intensity in the national scale,on the whole,with the increase of DMSP/OLS lighting intensity level,the surface temperature shows an increasing trend,and the increasing speed is inversely proportional to the monthly average surface temperature.In the 10th-level region with the highest light intensity,the surface temperature in cold months has decreased,which is partly affected by the light saturation effect and the cold-heat island effect in urban center.(3)As for the grading of low-resolution light radiation intensity in the national scale,with the increase of VIIRS/DNB light intensity,the surface temperature first increased;when the light intensity reached about 100×10-9wcm-2sr-1,the surface temperature began to show a discrete distribution.On the monthly time scale,the variation trend of the surface temperature within the light level is quite different,which is greatly affected by the seasonal,day-night thermal radiation characteristics and the complex and fragmented surface characteristics in the urban center.VIIRS/DNB classification can compensate for the saturation effect of DMSP/OLS in the high-luminance area,and achieve a fine depiction for the light environment of central area,which is helpful to show the fluctuation of surface temperature under the high heterogeneity characteristics of the complex structure in the urban center.(4)On the urban scale,the spatial distribution of NTL brightness in Beijing shows obvious characteristics of gradually increasing from periphery to center and point-like distribution of high NTL brightness.Low and medium NTL brightness mainly depends on population concentration and the density of residential living and working buildings,while high NTL brightness depends more on the development of urban economy and culture,the advancement and modernization of cities.In general,there is a positive correlation between the grayness and the brightness in Beijing.When the grayness aggregation density reaches 0.8,it is no longer an effective indicator to reflect the change of NTL brightness in Beijing.There are many factors influencing the urban heatness,and the change analysis is relatively complicated.As a whole,it is greatly affected by the surface coverage.From the suburbs to the urban center of Beijing,the surface temperature tends to rise,with scattered cold island areas in the urban center.Dense impervious surface has heating effect,and green space and parks have cooling effect on surface temperature.The locations with high light intensity but relatively low surface temperature are mainly found in transportation hubs such as airports and green parks in urban centers. |
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