Yin Xiao-Mei, Qiao Lin, Zhu Xiao-Wan, Guo Heng, Liu Xiang-Xue, Xiong Ya-Jun
Institute of Urban Meteorology, China Meteorological Administration, Beijing 100089, China.
Environment Meteorology Forecast Center of Beijing-Tianjin-Hebei, China Meteorological Administration, Beijing 100089, China.
Huan Jing Ke Xue. 2020 Nov 8;41(11):4844-4854. doi: 10.13227/j.hjkx.202003195.
In this study, the hourly meteorological factors and PM 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 were higher, and the relative humidity and dew point temperature were lower, when pollution occurred under the southerly wind, while the PM 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 PM 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.
本研究分析了2014 - 2019年北京逐小时气象因素和PM浓度，以探究污染盛行风向特征及相应的长期趋势。研究期间，北京67%的污染发生在南风和东风影响下，污染最易发生在冬季，其次是春季和秋季。冬、春、秋、夏的平均污染概率分别为45.2%、34.1%、32.1%和26.1%，南风和东风影响下的污染概率分别为47.0%、45.8%、39.7%和29.6%。在北京，南风出现频率更高，但东风控制下污染发生概率更高，春季差异最大为11.7%（2.8% - 18.6%），冬季差异最小为1.8%（ - 7.6% - 13.9%）。在过去六年中，南风和东风影响下污染概率分别以每年4.6% - 8.0%和5.5% - 7.9%的速率下降。这在中度及以上污染水平降低中得到明显体现。对两种风向条件下污染和气象因素的分析表明，南风影响下污染发生时，能见度、混合层高度、风速以及小时风速大于3m·s的频率更高，相对湿度和露点温度更低，而冬季污染的PM浓度高于东风，其他季节则显著低于东风。这些结果表明，南风影响下污染发生时，大气中污染物的承载能力和扩散能力略优于东风，东风影响下大气含水量增加更有利于污染的维持和加重。此外，在原始排放水平背景下，冬季增加城市供暖时，南风输送的气团可能更有利于PM浓度增加。此外，北京污染在春、夏、秋趋于“东风型”，但冬季仍为 “南风型”。
