出版社：Chinese Association for Aerosol Research in Taiwan
摘要：A severe haze-fog episode occurred in the Yangtze River Delta region of eastern China during22–30 November, 2018. In this period, the PM2.5 mass concentration and meteorologicalparameters at the surface were collected at the Station for Observing Regional Processes of theEarth System site in Nanjing. The vertical distributions of PM2.5, humidity and potentialtemperature below 500 m were observed simultaneously by an unmanned aerial vehicle, and theprofile of potential temperature at 1400 local standard time on each day was also observed byradiosonde at the same site. During the first four days, the PM2.5 mass concentration increased,the maximum convective planetary boundary layer height (CBLH) decreased, and the air humidityincreased. These are favorable conditions for fog formation. In the latter five days, fog formedon four days, with a lowering of the CBLH and a further increase in PM2.5 mass concentration. Wefound that the fog top cooling induced a potential temperature jump (i.e., sharp increase ofpotential temperature) with much warmer temperatures above the cloud top cooling and thatthis particular thermal structure was maintained until the end of the fog period, whichsignificantly suppressed the daytime development of the planetary boundary layer after fogdissipation. The fog-induced reduction of the CBLH further increased the PM2.5 massconcentration. We also found that the wet deposition of fog on PM2.5 was negligible. Thescavenging effect of fog on aerosols only acts during a fog period. When the fog dissipates, theaerosols are liberated from the fog droplets to the atmosphere.
关键词：Haze-fog episode;Potential temperature jump;Planetary boundary layer height;PM25
