HSRL vertical profiles featuring sustained low-level pollution transport and haze development. Atmospheric backscatter cross-section at 532 nm (a) and linear depolarization (b) observed by the HSRL in Seoul during the most significant period of sustained low-level pollution transport (25–26 May 2016). Altitude is provided above mean sea-level (MSL), which is an approximate AGL altitude (Seoul 38 m MSL). The approximate duration of each NASA DC-8 science flight is denoted by a brown arrow. DOI: https://doi.org/10.1525/elementa.395.f9