北京秋冬季近地层PM_(2.5)质量浓度垂直分布特征

Vertical Distributive Characters of PM_(2.5) at the Ground Layer in Autumn and Winter in Beijing

选取秋冬两季各14d对北京地区近地层ρ(PM2 5)垂直分布进行监测,获得ρ(PM2.5)垂直廓线;结合同步测得的气象数据,就气象因素对垂直分布的影响进行了分析;最终拟合了ρ(PM2.5)垂直廓线方程。研究表明:秋冬两季ρ(PM2 5)的垂直分布随高度增加而呈对数递减的规律;风速随高度的变化遵循对数规律;发生逆温时,大气层结稳定,垂直方向上的湍流受到抑制,风速与PM2 5逐时质量浓度在垂直方向的分布呈较好的线性关系,ρ(PM2 5)随高度改变呈显著的对数相关关系;而在非逆温的情况下,PM2 5逐时质量浓度垂直分布与风速线性相关的概率较小,质量浓度的垂直分布与高度的对数关系不显著。

Fourteen days were selected in the autumn and winter respectively to monitor the vertical distribution of PM_(2.5( mass concentration in the ground layer of the atmosphere in Beijing. Vertical profiles of PM_(2.5( mass concentration were obtained. Combined with the meteorological data measured simultaneously, the impact of meteorological factors on the vertical distribution was analyzed, and finally vertical profile fitting equations of PM_(2.5( mass concentration were got. It is demonstrated that the vertical distribution of PM_(2.5( mass concentration logarithmically decreases with the increase of the altitude obviously in the autumn and winter. The wind velocity varies with the altitude logarithmically. When there exists temperature inversion, the atmosphere stratification is stable and restrains the turbulence in the vertical direction, PM_(2.5( hourly mass concentrations in the vertical direction are in linearity with the wind speed, and thus PM_(2.5( mass concentration varies logarithmically with the altitude significantly. Under non temperature inversion conditions, the probability of PM_(2.5( hourly mas concentrations in the vertical direction being in linearity with the wind speed is small, and the logarithmic relationship between the mass concentration and the altitude is not significant.