Effects of Urban Heat Island on Summer High Temperatures in Beijing
Summer high temperature is a kind of urban severe weather in Beijing.In summer,the urban high temperature becomes more intense because of the urban heat island effect,it influences the civic living and consumptions seriously.For further understanding the mechanism of the city summer high temperature weather and improving the forecast,based on the automatic weather station data from 1998 t0 2002,the main distribution features of summer high temperature and the urban heat island in Beijing area are analyzed and the enhanced effects of urban heat island on summer high temperature are discussed.Moreover with high resolution mesoscale model MM5,the urban heat island effect on a representative high temperature weather process on July 12th,2002,is simulated.The results suggest that he main distribution features of the averaged highest temperature have a closely relationship with the terrain in Beijing area.The distributions of isothermohypse are along the tendency of the mountain and show the ladder shape features obviously.The distributions of urban heat island are related to the arrangement of the city functional area.There are two high temperature centers,one locates on the urban area around Lize Bridge,Guanyuan and Guanxiangtai where people act closely together and the other locates on the suburb close to urban area with intense industry activities in Shijingshan district.Also the results of EOF analysis on anomaly field of high temperature samples show that the urban area and the Huairou district are two places where the highest temperatures have relatively higher oscillation amplitude and prone to extremely high temperature cases.Averaged heat island index has the ascend tendency with the raise of ambient temperature.In the situations of extremely high temperatures above 39℃,averaged heat island index can reach 3.28℃ and it will have obviously enhanced effects on the intensity of urban summer high temperatures.The mesoscale model MM5 has the ability to simulate the extremely high temperature weather process in Beijing and show good simulation results of the range and intensity of summer urban heat island.The central intensity of simulated urban heat island reaches 3.5℃.At the same time,from the simulation the circulation feature of urban heat island and the air stream converged from the suburb to urban area can be seen on the surface layer obviously.But without urban land use in the sensitive experiment,the urban heat island can not be found.The difference with and without urban land use of surface sensible heat flux can reach above 300 W/m2 and the difference of surface latent heat flux goes to the opposite.From the results of the sensitive experiment,it shows a significant causefor the urban heat island effect which is the thermodynamic anomaly of different underlying surface features in Beijing urban area and the suburb.From the results,the enhanced effect of the urban heat island to summer high temperature is evident.
NETL
NSTL
万方数据
