Study On Urban Thermal Environment Based On Diurnal Temperature Range

Diurnal temperature range(includes land surface temperature diurnal range and near surface air temperature diurnal range)is an important meteorological parameter,which is a very important factor in the field of plant physiology,hydrology,meteorology and environmental science.Furthermore,diurnal temperature range controls such as photosynthesis,respiration,and land surface evapotranspiration and a series of mass and energy exchange processes on the surface of the Earth.To deep understanding and investigate land surface process and global change,high spatial and temporal resolution of diurnal temperature range is needed.Compare with the conventional weather observations,remote sensing provides a new effective approach for getting spatial-temporal diurnal temperature range information of wide range.Nowadays,the research of urban thermal environment mainly focused on surface heat island and canopy heat island.Surface temperature remote sensing products were widely used in the study of surface heat island simulation and monitoring.Compared with the widely used surface temperature remote sensing products in the study of city thermal environment,the near surface air temperature products are relatively few applications because of its inversion problem,station observation data is still an important data source of the city thermal environment research.Based on analysis of the current status of city thermal environment,Firstly,a method without need to obtain accurate day and night near surface air temperature respectively was proposed to obtain near surface air temperature diurnal range in this paper,difference of land surface temperature between day and night were introduced into the improved temperature vegetation index feature space based on remote sensing data.The model introduced land surface temperature difference between day and night(land surface temperature diurnal range,DTsR)and saturation vegetation index concept(max normalized differential vegetation index,NDVImax),through linear fitting of dry and wet edge and saturation vegetation index optimized selection,the near surface air temperature difference between day and night(near air temperature diurnal range,DTaR)based on remote sensing data were obtained,and verifying the result accuracy with the site observation data.Secondly,compared with the district administrative division and the land cover data,we analyzed the spatial and temporal distribution characteristics of the diurnal range of land surface temperature and near surface air temperature,the relationship between diurnal range of land surface temperature and near surface air temperature with land cover data was also analyzed.The spatial-temporal distribution characteristics of thermal environment in the study area are discussed from the perspective of new parameters and the combination of two dimensional angles,which extended the scope of application of thermal infrared remote sensing data.The conclusions of this study are as follows:1 The near surface air temperature diurnal range of Beijing city can be obtained from the improved temperature vegetation index feature space.Through site observation data validation,the observed value and measured value of RMSE is less than 1K when NDVI value at 0.725.2 The land surface temperature diurnal range is different at different time scales.The monthly scale is dominated by “inverted bell shaped” distribution,and the seasonal scale is mainly in the form of "L".In spatial distribution,the six areas of the city and suburban districts and counties as two groups,respectively,showed different distribution characteristics in space,including six districts of the city and suburban districts and counties in the surface temperature diurnal range distribution showed the opposite trend.3 During 2003-2012 s,the land surface temperature and near surface air temperature diurnal range of Beijing were fluctuating upward.The rising trend of the near surface air temperature diurnal range was more significant than land surface temperature diurnal range.In addition,the rise and decline of land surface temperature and near surface air temperature diurnal range in different districts were different.In the six city districts,the land surface temperature and near surface air temperature diurnal range in the six areas of the city were mainly downward.The decline trend of near surface air temperature diurnal range was more significant than land surface temperature diurnal range.4 During 2003-2012 s,the land surface temperature and near surface air temperature diurnal range of Beijing with similar characteristics in spatial distribution,with higher distribution land surface temperature and near surface air temperature diurnal range in urban area and with lower distribution of land surface temperature and near surface air temperature diurnal range in the Northwest Mountainous area and the area of Miyun reservoir.5 Combined with the land cover types,statistical analyzing showed that the highest land surface temperature and near surface air temperature diurnal range districted in the urban area,the lowest land surface temperature and near surface air temperature diurnal range districted in the water body area.At the same time,the land surface temperature diurnal range is greater than the near surface air temperature diurnal range.This distribution is consistent with the thermal physical properties of the underlying surface.