Impacts Of Anthropogenic Thermal Spatiotemporal Changes On Urban Local Climate And Its Mechanism

Rapid urbanization development affects the land-atmosphere process through changing the underlying surface,such as the urban geometry and building materials,which are important factors leading to the urban heat island and urban dry island effect.At the same time,the high-density and high-intensity human activities in urban area result in a large amount of anthropogenic heat(AH)emissions,which has an important impact on urban local climate.Thus,the spatiotemporal distribution of anthropogenic heat in Beijing area was calculated,based on a large scale urban consumption of energy model(LUCY),together with a great many parameter modifications in study area.The results show that the model gives reasonable diurnal cycle of AH,as well as daily,seasonal and interannual variations.Meanwhile,the spatial distribution of AH is consistent with population distribution.Therefore,LUCY could be used as AH input data for the mesoscale numerical weather prediction system WRF(Weather Research and Forecasting Model),for further analysis of the impact of anthropogenic heat on urban hydrothermal environment.This study coupled WRF with the AH results calculated by the LUCY model.On the one hand,the reasonability of the AH value will be evaluated indirectly by comparing the meteorological elements such as temperature,humidity and wind speed between numerical simulation and observation.On the other hand,whether AH with high spatial and temporal resolution is considered in WRF will affect simulation results,and the difference could be analyzed in this way.According to the results,the default AH values in the WRF were underestimated,which could not have a significant impact on sensible heat,temperature,humidity and wind speed.However,the influence of AH on these meteorological elements could be reflected through WRF-LUCY.Meanwhile,the WRFLUCY effectively corrected the simulation of the urban boundary layer since the AH missions intensified the urban-rural circulation and raised the urban boundary layer.Therefore,it is necessary to consider AH with high spatial and temporal resolution by WRF-LUCY model when analyzing the impact of the urbanization process on urban local climate.Further,this study analyzed the effects of AH value changes on urban local climates.The meteorological elements showed a nearly linear increase with the increase of AH value,and the growth rates were quite different between day and night.In addition,taking the central heating in winter as an example,the impact of a sudden increase of AH release on the urban climate environment was analyzed.The results showed that air temperature increases by more than 10 °C within 2 hours,but the temperature increase mainly occurred at night,while the humidity did not change significantly.At the same time,the warming effect will be weakened during precipitation.At last,the study took the construction of Tongzhou New City as an example,and analyzed the impact of urbanization process when considering both the changes of underlying surface and anthropogenic heat emissions.It is found that the impact of anthropogenic heat on Beijing local climate is far greater than the Tongzhou New City.Therefore,it is not scientific when only considering the change of the underlying surface in urbanization process analysis.During the precipitation period,the change of Tongzhou New Town and anthropogenic heat emissions will change the moving path of storm clouds and change the precipitation distribution of the city as well as its downwind areas,the impact period mainly occurred after the peak of the storm.