| 北京地区偏南风和偏东风条件下污染特征差异 |
| 摘要点击 2366 全文点击 1017 投稿时间：2020-03-18 修订日期：2020-05-20 |
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| 中文关键词 北京地区 PM2.5污染 偏东风 偏南风 特征差异 |
| 英文关键词 Beijing PM2.5 pollution easterly wind southerly wind characteristic differences |
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| 中文摘要 |
| 为探究污染的控制风向特征差异及其长期演变趋势，对2014~2019年北京地区逐小时气象要素和PM2.5浓度统计分析.结果表明，研究时段内北京地区67%的污染发生在偏南风和偏东风的控制下，且冬季最易出现污染，其次为春季和秋季，各自对应的冬、春、秋和夏季平均污染概率为45.2%、34.1%、32.1%和26.1%及47.0%、45.8%、39.7%和29.6%.北京偏南风频率更高，但偏东风下污染概率更大，污染差异在春季最明显11.7%（2.8%~18.6%），冬季最小1.8%（-7.6%~13.9%）.过去6 a，偏南风和偏东风下的污染概率分别以每年4.6%~8.0%和5.5%~7.9%的速度降低，很大程度体现在中度及以上程度污染占比的减少.偏南风下污染发生时，能见度和混合层高度偏高、风速偏大、小时风速≥3 m ·s-1的时次偏多、相对湿度和露点温度偏低，春季、夏季和秋季的PM2.5平均、峰值和75%百分位浓度显著低于偏东风控制下的污染，而冬季PM2.5浓度则偏高.这表明，污染发生时，偏南风下大气对污染物的承载和扩散能力略好于偏东风，且偏东风下大气含水量的增加有利于污染的维持和加重.而冬季，原有排放加上城市供暖的影响，偏南风输送的污染气团可能更有助于PM2.5浓度的升高.此外，春季、夏季和秋季的污染逐渐向"偏东风型"发展，但冬季一直保持"偏南风型"污染. |
| 英文摘要 |
| In this study, the hourly meteorological factors and PM2.5 concentrations during 2014-2019 in Beijing were analyzed, in order to explore the characteristics of the prevailing wind direction of pollution, and the corresponding long-term tendency. During the study period, 67% of pollution in Beijing occurred under the influence of southerly and easterly wind, and pollution was most likely to occur in winter, followed by spring and autumn. The average pollution probability of winter, spring, autumn and summer was 45.2%, 34.1%, 32.1%, and 26.1% and 47.0%, 45.8%, 39.7%, and 29.6% for southerly and easterly wind, respectively. In Beijing, the southerly wind appeared more frequently, but the pollution occurrence probability was higher under the control of easterly wind, with the maximum difference of 11.7% (2.8%-18.6%) in spring and the minimum difference of 1.8% (-7.6%-13.9%) in winter. During the past six years, the pollution probability decreased at a rate of 4.6%-8.0% and 5.5%-7.9% per year under the southerly and easterly wind influence, respectively. This was clearly reflected in reduced moderate and above levels of pollution. An analysis of both the pollution and meteorological factors under the two wind directions indicates that the visibility, mixing layer height, wind speed, and the frequency of hourly wind speed greater than 3 m·s-1 were higher, and the relative humidity and dew point temperature were lower, when pollution occurred under the southerly wind, while the PM2.5 concentration of pollution was higher in winter and significantly lower in other seasons compared to that of the easterly wind. These findings show that when pollution occurred under the southerly wind, the carrying capacity and diffusion capacity of pollutants in the atmosphere was slightly better than that of the easterly wind, and the increased atmospheric water content under the easterly wind was more conducive to the maintenance and aggravation of pollution. Moreover, under the background of original emission levels, when adding urban heating in winter, the air mass transported by the southerly wind may be more conducive to increased PM2.5 concentration. Furthermore, pollution in Beijing tended to be an "easterly wind type" in spring, summer and autumn, but remained a "southerly wind type" in winter. |
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