[Influence of Meteorological Conditions on Ozone Pollution at Shangdianzi Station Based on Weather Classification]

As a typical secondary pollutant, tropospheric ozone has become the primary pollutant in Beijing in spring and summer, and meteorological factors are one of the main factors affecting the change in concentration. Using atmospheric composition and meteorological observation data from 2008 to 2017, the weather types in Beijing were divided into six categories by Lamb classification and Mann-Whitney U test. Among these, the mean and extreme values of ozone concentration of SWW and C types at Shangdianzi station were the highest, and the highest frequency was from April to September, with a total of 47.4%. The main contribution weights of the two types were determined by a multiple stepwise regression equation. The southwest wind prevailed in 54.0% of SWW and C types, and the newly discharged pollutants and secondary aging air masses were continuously transported by the southwest air flow. The vertical velocity zero layer appeared near 850 hPa. The horizontal and vertical meteorological conditions were conducive to the transport, accumulation, and secondary generation of ozone. The northeast wind prevailed in 64.7% of AN and ESN types, and the air masses source was clean. The same subsidence movement and air divergence prevailed above 1000 hPa. The discharged pollutants can also be diluted and diffused quickly, and the ozone concentration was at a low value. Taking the NW type on May 3, 2015 as an example, although the northwest air flow prevailed on the ground, with clean source, the residual high concentration of ozone above the boundary layer was transported to the near ground through the vertical subsidence of the atmosphere, resulting in the high concentration of ozone on some days.