The impact of mesoscale circulations on boundary layer evolution and air quality during DISCOVER-AQ

The NASA DISCOVER-AQ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality) provided the opportunity to observe the influence of mesoscale circulations on the structure and evolution of the boundary and their associated effect on the air quality and aerosol trends within two urban airsheds. A network of ground-based instruments, soundings, and aerostat profiles captured significant modifications to BL structure as sea and bay breeze fronts, thunderstorm outflow boundaries, weak synoptic-scale fronts, and recirculation events impacted the region. The Millersville University Atmospheric Research and Aerostat Facility (MARAF) was used to obtain high vertical resolution profiles of the lower BL. A high load capacity aerostat carrying a tethersonde for conventional meteorological variables, O3 and NO/NOX criteria gas monitors and particle size distribution for air quality documented details of BL evolution to 500 m, while the NASA P3B aircraft spiraled above with a suite of instruments. Acoustic sodar provided continuous measurements of wind, virtual temperature and turbulence parameters. BL and aerosol layer depth was determined by an MPL4 micropulse Lidar, along with 4 m flux measurements of heat, momentum, moisture, CO2, and net radiation. Three case studies will be presented: 1) bay breeze convergence, recirculation, and ramp-up events in Edgewood, MD in July 2011; 2) aerosol transport over Central Valley, CA in January 2013; and sea-bay breeze interaction with a 200-plus ppbv O3 plume downwind of Houston, TX. These observations show a complex BL response to transformational air mass interactions.