Numerical Simulation Research On Meteorological Condition Of Typical Air Pollution Of Urumqi In Winter

Urumqi is experiencing serious air pollution and the situation of air quality are closely linked with local complicated meteorology condition and pollution sources situation.But due to the complex terrain of Urumqi area,the previous study based mostly on pollutant concentration of a finite number of observation sites and observation data of ground meteorological data,lack of regional representative,only cover limited time and space,also not comprehensive.The meteorological condition of a typical air pollution episode in Urumqi during January 10th to 15th in 2008 are studied by combining observation data and modeling of WRF meteorology model.From these analysis,we get the following conclusion:(1) Urumqi is experiencing serious air pollution and the situation of air quality are closely linked with local complicated meteorology condition and pollution sources situation. The air pollution episode usually occurred for low wind speed condition especially during the transition of wind directioin.There are high concentrations of pollution in Urumqi day and night.It's much affected by elevated source in the daytime,pollutant concentration reached different degree of high value;but at night,because of the "strangled-hold"effect of stable layer act on small and medim point pollution sources and area pollution sources,pollutant concentration maintain high levels.The low wind speed,even calm wind, against the spread of pollutants.(2) The very stable vertical temperature profile condition in upper air of is another important reason for serious air pollution in Urumqi. There were always upper-air inversions lasting over Urumqi during the day time of the episode, while inversion developed from surface during the night. The inversion strength of peak of pollutant concentration is higher than that of rise and decline phase of pollutant concentration.(3) Tian Mountain, Urumqi Valley, Jungar Basin, Turpan Basin created local circulations of valley and mountain breezes which created thick inversion, advection inversion in addition to the common radiation inversion, in Urumqi,. The thick inversions during the night also reduced the vertical exchange of momentum and increase the frequency of calm condition which reduced the transport of the local emitted air pollutants out of the Urumqi.