山区城市大气污染物传输扩散的数值模拟

利用Monte-Carlo模式预测了山区城市（贵阳市）的SO2地面浓度分布。为实现城市面源的数值模拟，对Monte-Carlo模式的浓度计量和水平扩散等方面做了改进。作为模式的输入参数，风场得自于对三维观测数据的客观分析，湍流的参数化公式按现场超声风速仪实测数据进行了调整和校核。其风廓线不完全遵循一般规律，在距地面50—500m之间，常出现一极值风层；该地区具有典型的山区小风扩散特征，稳定时u、v湍谱峰值明显地移向低频，水平扩散明显偏大。对模式做了理论和实验校核。在均匀湍流场条件下，和解析结果一致；冬季日平均浓度的预测值和监测值的相关系数为0.96。数值模拟结果表明:贵阳市冬季大气污染物的传输扩散主要依赖于强不稳定的天气条件和极值风层的扩散和通风作用。

Numerical Simulation of Air Pollutant Transport and Diffusion in Guiyang City

The Monte-Carlo model is used to predict the ground level concentration distribution (GLCD) of SO2 in mountainous city—Guiyang city. In order to accomplish the numerical simulation of the area source in the city, the concentration count and horizental diffusion in the Mont-Carlo model are studied. The wind fields used as the background or the input parameters are obtained from the objective analysis according to the three dimentional wind observations, and the turbulent parameters are determined by the parameterized formulas which have been adjusted with the local experimental data in Guiyang city. It is shown that the wind profile is not highly coincided with the ordinary features, there is usually an ‘extremum’ between the layers of 50 and 500m, there are the typical features of atmospheric diffusion under the light wind in Guiyang city, the spectral peak values of the velocity components u and v shift to the lower frequencies and the horizental diffusion remarkably increase. Additionally, the modeling verification both with other theories and the experiments have been done. The GLCD of homogeneous turbulence consists with that obtained from K-theory or Gaussian model. For the daily average values of GCLD in winter, the correlation coefficient between prediction and observation is 0.96. The GLCD simulated shows that the air-pollutant transport and diffusion in Guiyang city is mainly depended on the very unstable weather condition or the aeration effect of the ‘extremum’ wind layer.