A Numerical Study of the Urban Intensity Effect on Fog Evolution in the Beijing-Tianjin-Hebei Region

作     者：LIANG Zhao-Ming GAO Shou-Ting SUN Ji-Song 

作者机构：Laboratory of Cloud-Precipitation Physics and Severe Storms （LACS） Institute of Atmospheric Physics Chinese Academy of Sci- ences Beijing 100029 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Beijing Meteorological Bureau Beijing 100089 China 

出 版 物：《Atmospheric and Oceanic Science Letters》 (大气和海洋科学快报（英文版）)

年 卷 期：2012年第5卷第3期

页      面：240-245页

学科分类：081405[工学-防灾减灾工程及防护工程] 07[理学] 070601[理学-气象学] 08[工学] 0706[理学-大气科学] 0814[工学-土木工程] 

基　　金：supported by the National Science and Technology Pillar Program of China (Grant No.2008BAC37B01) the National Natural Science Foundation of China (Grant Nos. 40930950 and 40921160379) 

主　　题：numerical study urban intensity effect fog the Beijing-Tianjin-Hebei region 

摘      要：The influence of urban intensity on fog evolution in the Beijing-Tianjin-Hebei (BTH) region (China) is investigated numerically with the the Weather Research and Forecasting (WRF) model coupled with the urban canopy parameterization-building energy model (UCP- BEM) urban physics scheme. The experiments were designed with a focus on the influence of different urban intensities, which are represented by a different fractional coverage of natural land, buildings, and energy consumption inside buildings in an urban environment. The results of this study indicate that urban areas notably influence fog evolution when natural land is reduced to a small fraction (e.g., less than 10%). Developed land changes fog evolution through urban effects. Higher urban intensity (HUI) generally results in warmer temperatures and lower wind speeds throughout the day, while inhibiting morning specific humidity loss and afternoon specific humidity gain because of the HUI effect on surface heat flux, surface roughness, and surface moisture flux. HUI leads to later and weaker liquid water content formation, with a higher liquid water content base, primarily due to its effect on near surface temperatures. This finding implies that HUI may inhibit the conditions for fog formation. In addition, urban areas with equal natural and developed land coverage seem to greatly enhance the upward surface moisture flux, which is attributed to the combination of a relatively large potential evaporation on developed land and an ample moisture supply from natural land. As a result, the specific humidity increases in the afternoon.