Development and utilization of hexacopter unmanned aerial vehicle platform to characterize vertical distribution of boundary layer ozone in wintertime

Vertical observations of ozone play vital roles in understanding various atmospheric chemical processes in the boundary layer, particularly in winter. In this study, we attempted to measure vertical profiles of boundary layer ozone in the winter of 2018 over the Yangtze River Delta region of China, using a hexacopter unmanned aerial vehicle (UAV) platform. A commercial portable ozone monitor mounted in a thermal insulation box was attached to the UAV platform to conduct vertical ozone measurements. The results showed that the UAV platform could effectively capture the vertical variations of boundary layer ozone in wintertime. During the field campaign, surface ozone was in relatively low levels due to weak photochemical production. In the daytime, the ozone was well mixed within the boundary layer. At nighttime, uniform vertical distribution patterns and stratified distribution patterns were frequently obtained in ozone profiles below 500 m. Backward trajectories and wind profiles were used to investigate the horizontal and vertical transport of ozone. The stratified distribution patterns of ozone were closely associated with strong contemporary advection transport of ozone that was accompanied by enhanced winds aloft. Besides, strong wind shear enhanced the downward transport of ozone from the free troposphere into the boundary layer, leading to uniform vertical distribution patterns of boundary layer ozone and the elevated nocturnal surface ozone levels. The results of this study could provide insights into the understanding of the spatial variations and evolution patterns of boundary layer ozone in wintertime and constructing suitable boundary layer schemes in atmospheric chemical models.