Urban Thermal Environment Analysis And Simulation By Applying The Modified Building Energy Model Coupling With Community Land Model Urban Model

The urbanization causes one of the most significant land use and land cover changes(LUCC).Especially over the Second and Third tier cities in China,the great urbanization occurs during the past half century.It can significantly alter the radiative,thermal,moisture,and aerodynamic characteristics of the land surface.As aconsequence of these changes,urban climates can differ significantly from surrounding natural ecosystems,often resulting in urban heat islands.The dramatic changes in the thermal environment of urban surfaces could not only affect human health and wellbeing in terms of increased mortality and morbidity,but also alter components of the eco-environment,such as air and waterquality,biodiversity,and net primary production.To tests how the LUCC caused by urbanization affects the thermal environment in a typical third tier city in China,we built a Modified Building Energy Model(MBEM)and coupled it with the urban parameterization component of version 4.0 of the Community Land Model(CLM).Furthermore,the coupling system include the inventory approach for estimating transportation sector anthropogenic heat emissions.The MBEM was used to quantify the architectural responses of air conditioning system energy consumption and its consequent waste-heat emission to the urban canopy meteorological conditions;it was developed from the traditional BEM proposed by Kikegawa et al..Compared with the old BEM version,this new one has the following features:(1)it proposes a new approach for estimating indoor surface temperatures(roofs and walls surfaces)based on a support vector machine;(2)it uses a time-varying ventilation rate rather than an empirical constant to simulate the sensible heat exchange through ventilation;(3)it considers heat exchange between windows and the indoor air.Two goals can be achieved by using this numerical simulation system:(1)quantifying the emission of anthropogenic heat from buildings and(2)providing accurate parameters relating the urban energy balance to global climate models.To validate the accuracy of this coupling system(CLMU+MBEM)while avoiding disturbance by other anthropogenic heat(e.g.,traffic anthropogenic heat),we first solved the validation problem of urban fluxes at a suburban site(with relatively large nonurban coverage and significant spatial heterogeneity)by combining the Footprint model.Because it is difficult to directly validate the performance of the modified BEM;we solve this problem by evaluating the ability of the coupling system(CLMU+MBEM)to capture the sensible heat flux.Compared with the traditional BEM,the CLMU+MBEM showed a better performance through the reproduction of the daily variation of the sensible heat flux spatially-weight-averaged over the sparsely built-up area of the ‘Environment Synergic Observation Proving Ground' site in study area.In this study the coupling system was applied to quantitatively simulate and analyzed the spatial and temporal distributions and variations of the thermal environment in study area over the period of 2002-2015,under the rapid urbanization.The simulation results show that the development of urbanization is the main cause that lead to the increase of 2-m-height air temperature,the acceleration of sensible heat exchange between land and atmosphere,and the aggravation of urban heat island(UHI).Moreover,in order to understand the physical mechanisms that LUCC caused by urbanization affects the thermal environment,we analyze three aspects of anthropogenic LUCC,which affect the physical processes that shape the spatial and temporal pattern of study area's UHI.By applying the methods of statistical analysis,sensitivity analysis and Scenario simulation,we obtained main results as below:(1)there is a strong correlation between urban land cover and the UHI.(2)The relationship between air temperature and anthropogenic heat emission can be discussed as a kind of vicious cycle in which additional anthropogenic heat emission that results from increasing air conditioning system energy use due to higher air temperature of urban canopy could further intensify the high temperature environment itself.(3)The net long-wave radiation distribution was determined as an important driver setting the magnitude and diurnal cycle of the UHI.There are 65 figures,24 tables and 330 references in this paper.