Remote Sensing Technology Applications In The Mountainous Urban Heat Environment

Cities are a complex ecosystem where human system and natural system interact with each other.Ineffective energy produced by energy exchange between human and the city forms the urban thermal environment.With rapid urbanization,the type of land surface changes,which breaks the balance of city land-atmosphere energy and gives rise to a large number of thermal environment problems.Heat island effect has become an environment obstacle to city development in recent years and greatly affects the regional climate.Little work has been done on the thermal environment of mountain cities in the southwest featuring unique climate and geography.The main urban areas of Kunming are selected as the object of the detection in the research.In this paper,remote sensing technology is applied to complete inversion of regional land surface temperature and thermal environment analysis based on Landsat-5 TM data,with land surface temperature as an important indicator,so as to disclose the thermal environment characteristics of mountain cities located in the southwestern low-latitude plateau.In the light of the actual circumstances, a model of land surface temperature inversion for the mountain cities is established based on the surface emissivity ascertained and inversion of atmospheric parameters in accordance with the thermal radiation transfer equation by mono-window algorithm.The land surface temperature (LST) of the object area can be more accurately obtained by this inversion model as the accuracy of the model has been verified by sensitivity analysis of the inversion parameters.In addition,given that only one thermal infrared band in TM data contains information of thermal infrared radiation while data for other bands contain rich information of ground-object spectrum,the relative information has been referred to during the inversion of thermal environment.The land coverage conditions of underlying surface of the object area are extracted to ascertain the land surface emissivity.The existence of a large number of mixed pixel is determined by the image scale,on this basis,land coverage of underlying surface is categorized into impervious surface,vegetation and water.The categorization not only facilitates the inversion of temperature,but also provides important data for further analysis of the thermal environment of the object area.According to the results above,further analysis of the thermal environment has been done. In this work, density segmentation and profile line analysis are adopted to analyze the spatial pattern of the thermal environment.An approach is put forward to evaluate heat island effect of the object area,according to the thermal-field variation and to obtain the distribution of intensity for heat island effect.The regression analysis between land surface temperature and typical indexes such as normalized difference vegetation index(NDVI),normalized difference barren index(NDBI)and modified normalized difference water index(MNDWI)is completed.Results show that in addition to water,NDVI of other ground-object presents outstanding negative correlation with LST;NDVI of water is positively correlated with LST itself;NDBI is positively correlated with LST as well;and MNDWI is significantly negatively related to LST.The primary data about the contribution of three types of underlying surface to the thermal environment are obtained.Then further statistics on distribution of land coverage during different thermal range are collected,and typical regional land surface temperature changes is obtained by buffer analysis. The relation between area of the land coverage and land surface temperature is demonstrated to study the contribution of urban underlying surface allocation to the thermal environment.Conclusions as for the study:there is a significant heat island effect in Kunming area;the average temperature of study area is controlled by a large area of vegetation.Existence of considerable variability of land surface temperature of ground-object can't be disregarded. Building land consist of impervious surface is the major cause of rise in land surface temperature; water and vegetation cover are beneficial to bring down the temperature;and the cooling effect of water is better than the vegetation.Reasonable layout of urban underlying surface is an effective measure to reduce the heat island effect.Finally,evaluation of present thermal environment status for the object area based on results of research is presented as well as proposals to improve the thermal environment.