The Impact of Anthropogenic Heat on Urban Boundary Layer Structure
人为热对城市边界层结构影响研究

The urbanization is a process that the human being changes the local natural surface characteristics widely and dramatically.This process will impact local atmospheric environment greatly.To understand the urbanization's effect on local urban boundary layer will show its great value in urban weather/climate study,urban environmental protection,urban design and construction,urban disaster-prevention,and will help us improve the residential environment and residential quality in urban area.A numerical simulation model is used in this paper to investigate the effect of the inhomogeneity of urban anthropogenic heat source on the exchanges of energy and material between surface and atmospheric system,and its impacts on urban boundary layer structures.To study the anthropogenic heat affecting the urban boundary layer structures,Hangzhou is taken as an example.A new anthropogenic heat source scheme is developed in the regional boundary layer numerical model(RBLM).In this new scheme,the urban anthropogenic heat source is distributed into different model layers.The lower layer heat release is added into the surface energy budget and the upper layer anthropogenic heat release is coupled into the atmosphere energy equations and its vertical distribution is related with the urban building distribution feature,including building height and density and the diurnal change of anthropogenic heat release is included in this scheme.The numerical simulation results show that this scheme can describe the anthropogenic heat release process better than former schemes and the simulated temperatures,wind directions,wind speeds are closer to the observation data.In the former anthropogenic heat release scheme all of the heat is added into the surface,this leads to the increasing of temperature and turbulence energy,and in the daytime this impact will be transported to upper atmosphere due to the strong turbulence and the increase of atmospheric temperature and turbulence is not obvious in lower air layer.The atmospheric instability increases and the boundary layer height increases by 400 m,the vertical speed over urban area is increased and urban heat island density is strengthened.In the nighttime the impact of anthropogenic heat is more obvious than in the daytime without the solar radiation heating.In the cases of the new scheme turbulence energy in lower layers increases by 40% and the atmospheric stability decreases.In general,the simulation results with the new anthropogenic heat release scheme show that the anthropogenic heat affects the urban boundary layer structure more greatly in the nighttime than in the daytime.And this impact is largest in winter,less in spring and autumn and weakest in summer.The reason may depend on that,in the surface energy budget the solar radiation is the main energy source,while anthropogenic heat is an important but not primary source.Compared with the diurnal and seasonal change of solar radiation,the anthropogenic heat release is a