The Impact Of The Terrain Effect On Land Surface Temperature Variation Based On Landsat-8 Observations In Mountainous Areas

In order to utilize mountain resources and energy,research on parameters of mountain surface(such as Land Surface Temperature(LST),soil moisture)is quite necessary.Among these,LST is a key surface parameter in mountain environment research,so the study of mountain LST is particularly important.However,the mountain terrain is extremely complex and there are many factors that affect the LST of the mountain,such as topographic conditions,vegetation,and solar radiation received at the surface.They directly or indirectly affect the changes in the LST of the mountain.Therefore,it is a very important step to study the relationship between terrain and LST in the researches of mountainous environment.Since mountainous terrain varies a lot in a small range of region,satellite images of high resolution provide the possibility for the study.Based on the previous research,this paper has further improved its research methods.For example,only a single research area was selected from different previous studies.In this paper,two research areas with large latitude spans and different climatic zones were selected while analyzing the relationship between topography and LST,it is also possible to compare the effects of latitude,seasons,etc.on LST.Considering that the larger the study area is the more uncertain factors.Therefore,in this paper,the complete satellite images are not used for research.Instead,two small watersheds with different geographical environments are selected to study the surface temperature.In this thesis,by controlling the effect of a certain terrain factor on surface temperature,the influence of another factor on surface temperature is studied.Statistical analysis,regression analysis and other mathematical analysis methods are used to analyze the surface temperature influence factors from both qualitative and quantitative aspects.The conclusions are as follows:(1)Land surface temperature has a close relationship with altitude,and the change of land surface temperature with altitude is similar to the change of air temperature with altitude.If the altitude changes by 1 km,the land surface temperature will accordingly rise or fall by 7.6K to 13.8K.(2)In different seasons,the influence of slope aspect on land surface temperature has a similar pattern of change in winter and summer.The reason for slope aspect affecting land surface temperature is mainly due to different solar radiation intensity received from different aspect,and areas which are opposite to the slope aspect of sunreceives more solar radiation energy.(3)Gradient is also a topographic factor that directly influences how much solar radiation is received by the Surface.Different gradients affect the angle at which the sun's rays enter the surface,further affect the amount of solar radiation received at the surface,and ultimately result in the huge difference of land surface temperature even in the same altitude.(4)Vegetation also plays a very important role in the change of land surface temperature.Vegetation not only controls the surface temperature through the surface energy balance,but also the coverage of the vegetation affects the sensor's direct observation of the exposed surface,and the difference in radiation temperature between the soil and the vegetation canopy will also affect the spatially integrated surface temperature.(5)Since land surface temperature rise is an accumulative process of receiving solar radiation at the surface,we use the cumulative solar radiation value of each pixel to replace the instantaneous solar radiation of the pixel at the time of satellite transit.By analyzing the spatial and time between cumulative solar radiation and land surface temperature,it was found that cumulative solar radiation has a decisive influence on land surface temperature.