Vertical profiles of particle light extinction coefficient in the lower troposphere in Shanghai in winter based on tethered airship measurements

A cavity attenuated phase shift single scattering albedo monitor was set up on a tethered airship platform to study the vertical profiles of particle light extinction coefficient (b est ) in the lower troposphere (<1000 m) in Shanghai during 12-29 December 2015. Clear transition heights (THs) for vertical profiles of b est during the polluted days (PM2.5> 75 mu g m(-3)) were observed below 1000 m. The vertical differences of b(ext) were highly dynamic as the vertical variation in b(ext) was significant by as much as 605 Mm(-1). The TH was observed mostly at about 100-200 m, and 450-650 m during night and daytime, respectively, and was in a wide range of similar to 50-900 m during 15:00-22:00 due to the low boundary layer and/or the transport of pollutants. In particular, the TH was consistently below 500 m throughout the day during highly polluted haze episodes, highlighting the important role of a stagnant atmosphere situation for high concentrations of PM2.5. The vertical distribution of b(ext) did not have a constant rule with respect to relative humidity and wind. Sometimes, peak values of b est at similar to 350 m and 500 m during daytime were caused by enhanced regional transport. During stagnant and highly polluted situations or well-mixed clean days, b(est) was usually uniformly distributed below and above the TH, respectively, although b(est) was much smaller above the TH. For other situations, local emissions, pollutant transport, and the physical and chemical characteristics of aerosols resulted in highly dynamic vertical profiles of b(ext). (C) 2019 Elsevier Ltd. All rights reserved.