Research On Quantitative Estimation Of Anthropogenic Heat In Hangzhou Based On Landsat Remote Sensing Data

Since the industrial revolution, cities have been the areas where human activities are the most frequent, and the space where the material, energy and information exchange most actively. Anthropogenic heat flux (AHF) is the heat flux that generated by urban human activities and released into the atmosphere. Most researches on urban heat island ignore this part of heat in the past flux due to anthropogenic heat emission was small. But in recent years, with the increase of urban energy consumption anthropogenic heat emission has become an important factor of aggravating urban heat island effect. Because studies on anthropogenic heat are still in the exploratory phase, quantitative estimation and analysis on anthropogenic heat has important theoretical and practical significance.With the review of domestic and foreign researches related to anthropogenic heat, and through comparing energy inventory method with surface energy balance equation method, we find that the estimation method using remote sensing based on energy balance is more close to the actual spatial distribution and numerical value. Using Landsat TM remote sensing images of the study area in year1991,2000and2010, such surface parameters as NDVI, MNDWI, surface albedo, emissivity and temperature are calculated, and the land cover classification information of three years are extracted. A series of meteorological parameters were calculated with the meteorological data, including the aerodynamic resistance, the stomatal resistance, atmospheric emissivity and atmospheric transmittance and so on. Based on urban surface energy balance equation, and using these surface remote-sensing parameters and meteorological parameters, surface net radiation, sensible heat flux, latent heat flux and ground heat flux are calculated, finally the spatial distribution images in different years of anthropogenic heat flux are received. In present study, the maximum values of anthropogenic heat in the study area was83.63Wm-2in1991,147.68Wm-2in2000, and287.17Wm-2in2010. Using GIS spatial analysis function, the average values of anthropogenic heat was obtained, which shows18.76Wm-2in1991,27.5Wm-2in2000, and125.66wm-2in2010. Anthropogenic heat release increased rapidly in the period of2000to2010.Using the method combined with quantitative and qualitative methods, and on the basis of analysis on spatial and temporal variation of anthropogenic heat in Hangzhou, the relationship between anthropogenic heat and social economy, land expansion and impervious surface changes are analyzed. It is found that urban anthropogenic heat flux has positive correlation with the density of urban population, GDP, impervious surface ratio, which has no absolute relationship with the urban construction land area. So, activity changes inside the land use are the main cause of anthropogenic heat rising in values. By extracting the LST curve and AHF curve from urban south-north and east-west profile lines, we found that the urban anthropogenic heat flux and surface temperature changing trends are basically the same and urban anthropogenic heat emissions having warming effect on the earth’s surface, which proves that the anthropogenic heat emissions is one of the main reasons of aggravating urban heat island effect. Finally, we propose some useful mitigation measures and recommendations for different anthropogenic heat sources.