【作者】 王永红；

【导师】 冯贵颖； 薛志钢；

【作者基本信息】 西北农林科技大学 ， 环境工程， 2008， 硕士

【摘要】 中尺度大气数值模式的建立及其与大气污染扩散模式的衔接是数值模拟的重要分支,也是目前城市空气污染问题的主要研究方法。边界层参数化是数值模式的一个重要组成部分,较真实的模拟边界层中的湍流运动,对于大气污染物的分布扩散及空气质量模式的运行效果具有重要意义。“乌鲁木齐市大气污染成因及防治对策研究”即是以乌鲁木齐市为研究对象,探讨乌鲁木齐市冬季重污染问题及其成因,了解地区污染的分布形成规律。本研究是该课题的组成部分,利用MM5中尺度气象模式和CALPUFF空气质量模式,采用不同的边界层参数化方案,模拟区域的流场和湍流运动,比较不同边界层参数化方案下大气污染物的浓度分布情况。主要结论如下:（1）Blackadar PBL方案、Eta PBL、MRF PBL和Gayno-Seaman PBL参数化方案水平风场模拟结果与监测站的实测资料吻合较好。夜间,不同方案间模拟结果相差较小,垂直剖面风矢量图中各高度层风向变换趋势大致相同。白天,4种方案模拟结果差别较大,主要体现在风速最大值出现的位置和影响范围不同。4种方案对于高空风场的模拟存在较大差异,表现在风向转换和风速两方面;（2）对于风速廓线的模拟,各方案间存在较大差异,但变化趋势大致相同。近地面至300m左右高度,风速值变化较小,从300m高度层开始,风速变化显著。在夜间层结稳定情况下,低高度处风速随高度先变小,随后快速增加,达到一定高度处风速达最大,在白天不稳定层结情况下,风速先变大,后变小,最后随高度趋于均匀。总体来看,风速变化不是很规则,这与该地区大气扰动较大有关;（3）各方案模拟的温度层结大体结构相同,但在对流层中低层却存在明显差异;无论白天、夜间,温度都随高度增加而升高较快,出现逆温,夜晚逆温强度强于白天,400m高度开始,温度递减,各方案模拟结果大致相似,与乌鲁木齐长期监测资料吻合;（4）三个监测站点的SO₂浓度值变化较大,早晨浓度最大,中午最小,傍晚介于两者之间;SO₂模拟值中午时段较高,而早晚较低,这是因为中午时段对流运动及垂直扩散的加强导致了高架源排放污染物向近地面层的下泄,而早晚稳定的大气层结不利于高空污染物向地面的转移;（5）PM₁₀模拟浓度值随路面机动车流量的变化而变化,并在上下班高峰期呈现峰值,各方案模拟浓度值白天均高于夜晚及凌晨时段;（6）4种方案对于SO₂和PM₁₀的模拟结果随时间的变化趋势大致相同。特别是夜晚及清晨模拟差异较小,但在15¹8时往往存在较大差异,Gayon-Seaman PBL方案和Eta PBL方案对应的模拟值明显高于其他两种方案;（7）4种方案中,Eta PBL方案和Gayno-Seaman PBL方案模拟高空及近地面风速较小,各点源排放污染物在较大范围内均匀散布开来,仅在点源附近表现出较高浓度。Blackadar PBL方案和MRF PBL方案等值线密集,污染物在水平输送气流的影响下,常可导致下风向地区大范围高浓度值的出现;（8）采用MM5输出的气象场资料进行空气质量数值模拟,可以在一定程度上较好地反映重污染天气过程中,SO₂和PM₁₀等常规污染物的浓度变化特征,特别是日变化特征。但由于研究工作中考虑的源的数量、种类的局限性,模拟的浓度值与实测值相比偏低。更多还原

【Abstract】 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.更多还原