关键词: 大雾, 东南大风, 逆温, 湿度, 诊断

Abstract:

Based on the NCEP reanalysis grid ( 1° × 1°) data，conventional observations，numerical forecast products as well as wind profiler data，a large scale fog weather event occurred in the central Urumqi on 25 December 2011 was investigated from circulation background，temperature and humidity feature，stratification condition，the surface layer wind field features． The results show that the warm ridge after the upper trough，no obvious cold air activities over middle latitude，and stable atmospheric circulation background were advantageous to temperature inversion formation，and the formation and maintenance of the temperature inversion in the boundary layer played an important role on the development and sustentation of the fog weather． When the heavy fog occurred，the southeast wind was more than 20 m·s － 1 ，meanwhile southeast gale from south suburbs and northern wind from urban area formed strong convergence around surface layer over southern urban area，which was not conducive to horizontal and vertical diffusion of urban pollutants． The heavy fog also tended to occur towards the cold air side near the convergence of the surface． Southeast gale was an important index of wind field for the heavy fog event in the central Urumqi． Wind profiler data and EC numerical forecast production can exactly provide forecasting in advance for the southeast gale in south suburbs of Urumqi，and were helpful to predict the generation，development and dissipation of fog，which could reduce the damage caused by the heavy fog event．

Key words:

heavy fog, southeast wind, temperature inversion, humidity