新疆天山北坡低层大气稀释扩散能力的季节性差异和量化研究

随着我国重点区域空气质量水平的整体改善，新疆天山北坡的污染问题日显突出. 为了探究当地低层大气稀释扩散能力的季节性差异及其对污染的影响，综合运用多种观测资料，对PM_2.5污染和气象条件的季节性差异及二者之间的联系进行了系统分析，并利用区域空气质量模型开展数值试验，对低层大气稀释扩散能力进行了量化. 结果表明:①天山北坡主要城市冬季(12月—翌年1月)和春夏季(5—8月)PM_2.5浓度最大可相差10.8倍. 对环流形势、地面气象要素、下垫面和低层大气层结等气象条件分析发现，低层大气稀释扩散能力是造成PM_2.5浓度差异较大的首要外因. ②天山北坡主要城市春夏季的低层大气稀释扩散能力远高于冬季，最高为冬季的4.9倍；稀释扩散能力的逐月变化表明，稀释扩散能力最强和最弱月份最大相差5.6倍. 而同处北方的京津冀地区，春夏季与冬季最大相差2.0倍. 研究显示，合理利用低层大气稀释扩散能力的季节性差异，施行系统性的错峰生产，竭力减少冬季大气污染物排放，将是改善天山北坡城市空气质量的有效途径. 

Seasonal Variability of Ventilation in the Low Atmosphere over the North Slope of Tianshan Mountains and Its Quantification

With the improvement of other key regions of China, the pollution problem on the Northern Slope of Tianshan Mountains has become increasingly prominent. In order to investigate the seasonal variation of ventilation capacity and its effect on local pollution, the seasonal variation of PM_2.5 pollution and meteorological conditions, along with their relationship, were analyzed by using multi-observation datasets synergistically. Meanwhile, the seasonal changes of ventilation were quantified by a regional air quality model. It was found that the PM_2.5 concentration in winter (from December to January) can reach 10.8 times that of spring to summer months (from May to August). The analysis of meteorological elements revealed that the seasonal variation of ventilation capacity was the primary external factor responsible for the large concentration difference in low atmosphere. The simulation results indicated that the ventilation capacity of some major cities in spring and summer was much stronger than that in winter, which could be 4.9 times the effects in winter. In terms of monthly variation, the strongest monthly mean ventilation was up to a factor of 5.6 of that in the weakest month. Although the Beijing-Tianjin-Hebei Region is at similar latitude as the Northern Slope of Tianshan Mountains, the difference in ventilation capacity between spring-summer and winter was less than 2.0. Thus, minimizing winter emissions through shifting the peak production among seasons will be an efficient way to improve air quality on the Northern Slope of Tianshan Mountains.