Abstract:

Based on meteorological observation data,Europe Center (EC)-Interim reanalysis data,L-band radar sounding data and air quality monitoring data,the three heavy pollution events that occurred in He'nan province from November 27 to December 25 were comparatively analyzed,from the perspective of the pollution scope,time,intensity and primary pollutants as well as meteorological conditions.The results show that smooth circulation,weak pressure gradient,high humidity,small wind speed,and temperature inversion are all beneficial to the formation of heavy pollution.He'nan province is controlled by a weak ridge at 500 hPa during the most heavily polluted days in the event I and II and controlled by the northwesterly flows behind a trough in the event III.Northerly winds are favorable to transport pollutants from the north to the south and result in a large area of heavy pollution.All the three events end up with the westerly cold air flows.PM_2.5 concentration has a lead-lag correlation with wind speed,humidity,24-h temperature variation,and 24-h pressure variation,with the best correlation of 4-h forward for wind speed,1-h forward for humidity,10-h forward for temperature variation and 19-h forward for pressure variation.Temperature inversion exists in the boundary layer during the three events.A temperature inversion occurs both near the surface and in the upper levels during the most period in the event I,while it occurs only near the surface in the event II and III.The air is relatively dry at high altitudes and moist at low altitudes in the event I;such characteristics are not observed in the event II and III.The pollutants are removed from in the middle and western regions at first,followed by the northern region,Nanyang area,and the eastern region in the event II and III,while in the event I,air pollutants in the northern region are removed firstly.

Key words: Air quality index(AQI), Primary pollutant, Meteorological condition, Correlation, Transport