Spatial Temporal Variation Characteristics And Its Influencing Factors Of Thermal Environment In The Urban Area Of Shanghai

Under the background of global climate change, high temperature disasters are affecting the production and daily life. Therefore, how to accurately characterize the urban evolution and temporal factors of thermal environment and explore improvements have important theoretical and practical significance. In this paper, Shanghai urban area under rapid urbanization is chosen as an example, based on the analysis of extreme high temperature change trends in recent years, the spatial and temporal characteristic of thermal environment (including land surface temperature and air temperature) are analysied by the use of remote sensing and GIS spatial analysis. Meanwhile, the influence factor of thermal environment is discussed from natural and human aspects. On this basis, it is explored how to improve thermal environment by adjusting the urban pattern. This paper includes the following contents and conclusions:(1) The change trend research of extreme high temperature event in recent years in Shanghai:Based on the meteorological data from 1960 to 2013 in Shanghai, the change trend characteric of extreme high temperature event is analysed through the highest temperature, high temperature days, warm nights, heat wave indice, hot days and generalized extreme value distribution. The results show:in recent years, the daily highest temperature in summer has significantly increased, warm nights and heat wave indice has increased obviously, which reach a maximum value especially in 2013. The research of hot days and generalized extreme value distribution indicate that there are two change trends around the year of 1976. The extreme high temperature event is most significant in the urban areas of Shanghai, and Fengxian district and Jinshan district have the least significant extreme high temperature phenomenon. Different indicators can comprehensively characterize extreme heat extreme high temperature event trends.(2) The research of characteristics of land surface temperature in Shanghai:Based on Landsat satellite data, the land surface temperature field of August 11, 1989, September 18,2000 and August 13,2013 are got by the use of single-channel inversion algorithm. On this basis, the spatial and temporal variation characteristics of land surface temperature in the past 25 years are comprehensively analysized and completely descripted through zoning analysis, centroid variation analysis, landscape pattern analysis and spatial autocorrelation analysis. Furthermore, the influencing factors of land surface temperature in Shanghai are explored from two aspects (including nature and social factors). The results show:the city center has a relatively high temperature with a characterist of more accumulation and expansion. The strength of the thermal environment in Shanghai has a major shift to the south. The urban land will enhance urban thermal environment and water and vegetation contribute to the improvement of urban thermal environment.(3) The research of spatial and temporal distribution characteristics of extreme high temperature in Shanghai:Based on Landsat OLI remote sensing data and meteorological data of 12 July 2013,13 August 2013 and 29 August 2013 in Shanghai, the characteristics of the spatial distribution of temperature daily temperature are assessed by the introduction of spatial regression method. The results show that:the predictive model of least squares regression building based on three indicators (including surface temperature, normalized moisture index and solar radiation) can better predict air temperature in the hot days in Shanghai (RMSE=1.75℃, R2=0.92). Meanwhile, a continuous spatial distribution of urban heat environment will be got completely. The urban thermal environment is non-balanced, diversity and fragmentation. Besides, the similar spatial patterns have spatial aggregation characteristic. The low temperature area (maximum temperature lower than 35℃) mainly distribute in the southern area and the water area of Shanghai. The high temperature area (maximum temperature not lower than 38℃) mainly distribute in urban/suburban area. In future, it will be helpful for urban construction by the reasonable urban planning, control the scale of urban development, increase the green area and other measures to mitigate the disaster caused by extreme high temperature weather.