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利用佛山地区2013年12月大气边界层观测试验得到的垂直风温资料和相应逐日AQI资料、逐时PM_(2.5)浓度资料,研究了佛山地区大气边界层垂直风温结构对空气质量的影响.结果表明:佛山地区干季持续存在的逆温结构是导致PM_(2.5)污染较重的重要原因.干季污染日近60%的最低逆温层高度低于1000 m,而非污染日低于1000 m的最低逆温层仅占36%,污染日佛山贴地逆温频率高达31.2%.逆温层出现高度较低,将污染物压缩积累在贴地层大气中导致污染较重.在大陆冷高压控制下,佛山地区的边界层结构演化非常典型,最大边界层高度和最大边界层通风量表现出了显著相关,污染日日平均边界层高度始终维持在较低的水平,多数时候不足500 m,最大边界层高度则大部分小于1000 m,日平均边界层通风量主要分布在500~1500 m~2·s~(-1)之间,在极端情况下甚至不足300 m~2·s~(-1),最大边界层通风量大部分处于1500~5000 m~2·s~(-1)之间,导致污染物始终聚集在较低的大气边界层内,使得PM_(2.5)浓度长时间维持在较高的污染水平.佛山地区风场存在显著的3层结构,较小的底层风速意味着大气的输送和扩散能力较弱,高度较低的中层使得污染物进一步被压缩累积在大气底层,垂直风场的不稳定性使得污染日佛山地区局地回流活跃,回流(RF)指数极小值多分布在0.2~0.4之间,污染日RF指数普遍小于非污染日,垂直风场的有效输送能力被显著削弱.
Using the vertical air temperature data and the corresponding daily AQI data obtained from the observation of the atmospheric boundary layer in December 2013 in Foshan region, the temporal PM_ (2.5) concentration data were used to study the effect of vertical air temperature structure on the air quality in the atmospheric boundary layer in Foshan. The results show that the inversion temperature structure persisting in the dry seasons in Foshan is the most important cause for the heavy pollution of PM 2.5, and the lowest inversion temperature of nearly 60% in the dry season is less than 1000 m, while the non-pollution days are lower than The minimum temperature inversion layer of 1000 m accounted for only 36% of the total, and the frequency of inversion in Foshan was up to 31.2% on the day of pollution. The inversion layer was relatively low in height and the pollutants were compressed and accumulated in the stratospheric atmosphere, resulting in heavy pollution. Under the control of high pressure, the evolution of the boundary layer structure in Foshan is very typical. The maximum boundary layer height and the maximum boundary layer ventilation show a significant correlation. The daily average pollution boundary height always remains at a relatively low level, most of which is less than 500 m , The maximum boundary layer height is mostly less than 1000 m, the average daily average boundary layer ventilation is mainly distributed in the range of 500 ~ 1500 m ~ 2 · s ~ (-1), and in extreme cases even less than 300 m ~ 2 · s ~ (-1), most of the maximum boundary layer ventilation Which is between 1500 ~ 5000 m ~ 2 · s ~ (-1), causing the pollutants to accumulate in the lower atmospheric boundary layer all the time, so that the concentration of PM_ (2.5) is maintained at a relatively high level for a long time. There is a significant three-layer structure in the field. The smaller bottom wind speed means weaker transport and diffusion of the atmosphere. The lower middle layer causes the pollutants to be further compressed and accumulated in the bottom of the atmosphere. The instability of the vertical wind field makes the pollution day In Foshan, the local reflux was active, and the minimum of return index (RF) index was distributed between 0.2 and 0.4. The RF index of pollution day was generally less than that of non-pollution day, and the effective transportation capacity of vertical wind field was significantly weakened.