Comparison of Observed and Simulated Boundary Layer Height Estimates during Discover-Aq July 2011

The first deployment of the NASA Earth Venture -1 DISCOVER-AQ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality) project was conducted during July 2011 in the Baltimore-Washington region. The P-3B aircraft provided in situ vertical profiles of meteorological quantities, trace gases, and aerosols over six Maryland Department of the Environment (MDE) air quality monitoring sites over fourteen flight days. The UC-12 aircraft provided continuous remote sensing observations of aerosols over its flight track with the High Spectral Resolution Lidar (HSRL). Additionally, several MDE sites were equipped with the ground-based Micro-Pulse Lidar (MPL) instrument, also providing continuous, remotely sensed aerosol observations, and two sites launched ozonesondes during the campaign. A major goal of DISCOVER-AQ is to understand the processes linking trace gas column abundances to surface concentrations, including vertical mixing in the planetary boundary layer (PBL). In support of this goal, estimates of the PBL height output by the WRF/CMAQ model system (ACM2 PBL scheme and Pleim-Xiu surface layer scheme) were compared to observational estimates of PBL height during the July 2011 deployment. WRF/CMAQ typically demonstrated a high bias in PBL height relative to the meteorological PBL height estimates (those based on the potential temperature profile measured by the P-3B or ozonesondes), while the model demonstrated a low bias relative to PBL height estimates based on the aerosol backscatter profile (HSRL and MPL data). Additionally, the model tended to overpredict the PBL height on days when the PBL was well mixed, and underpredicted when the PBL was poorly mixed. Preliminary results from an intercomparison of the WRF model run with six different PBL schemes (ACM2, YSU, MYJ, MYNN, QNSE, and BouLac schemes) will also be presented.