| Establishment of mesoscale meteorological simulation system, as well as its linking up to the diffusion models of atmospheric pollution, is an important embranchment of numerical simulation. Furthermore, it's also the way mostly used in dealing with urban air pollution. Atmospheric boundary layer parameterization which plays an important part in simulating the turbulence in the boundary layer truly is an essential part of the numerical model and plays a significant role in the effect of urban air quality model. Dealing with Urumchi city, the project -'The major reasons and causes of air pollution in Urumchi as well as the ways and measures to prevent its pollution'investigates the main causes of the heavy pollution in winter time in Urumchi and the distributing and formation characteristics of regional pollution. As one component part of the subject, this study mainly simulates the meteorological field and the turbulence in Urumchi with different boundary layer parameterization schemes of MM5. Furthermore, with the help of CALPUFF, we also do some comparation between the distribution situation of concentration with different output from MM5. Main conclusions are as follows:(1)Blackadar PBL, Eta PBL, MRF PBL and Gayno-Seaman PBL of the MM5 are carried out to calculate the horizontal wind field. It shows that results from the four schemes tallies well with the actually measured data. At night, there is little difference between these schemes while in the day time, the location and incidence of maximum wind speed differ widely. Wind direction and wind speed are also different in upper air according to the four schemes.(2)Profiles of wind speed differ widely from one another according to the four schemes, but all change in the similar trendency. The value of wind speed changes a little from the surface to the 300m level,but changes remarkably hyper-300m. In the evening, wind speed diminishes at first and then increases quickly in the low level. In the day time, it is quite the opposite. On the whole, changes of wind speed is not very regular,responsing to the turbulence in this area.(3)Simulated structures of the temperature layer are similar in the four schemes. The temperature increases quickly with the height all day long. That is to say, temperature inversion is frequent. The intension of inversion is stronger in the evening. The temperatuer begins to decrease at 400m level.(4)With its maximum value in the morning and minimum value at noon, the measured concentration of SO2 changes greatly. On the contrary, the simulated concentration of SO2 is highest. The reason is that with the intensification of convection and uprightness movements at noon, pollutants emitted from high chimneys are more easily to go down to the surface level.(5)The simulated concentration of PM10 varies with the runoff of vehicles on the road. The peak value appears at the up and off duty time. The simulated concentration in the day time is larger than that in the evening and that at the wee hours.(6)The simulated concentration of SO2 and PM10 all change in the similar trendency according to the four schemes, especially in the evening and at the wee hours. But the simulated concentration differs greatly from 15 to 18. Gayon-Seaman PBL and Eta PBL have a relative high value than the other two schemes.(7)The simulated values of wind speed in Eta PBL and Gayno-Seaman PBL are relatively smaller. Air pollutants emitted from emission sources spread equably within a large limits. Under the influence of horizontal transport currents, leeward districts often have a high concentration of air pollutants.(8)To a certain extent, numerical simulation of urban air quality with the meteorological output from MM5 can reflect the course of heavy pollution, as well as the changing characteristics of SO2 and PM10 concentration. But the simulated values in the study are on the low side owing to the lack of emission sources.
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