An Ad-Hoc PBL variability experiment over the Washington, DC area

NOAA develops decision support systems to aid decision makers in the event that significant amounts of wild fire smoke, dust or harmful toxic materials are released to the atmosphere. Specifically, NWS Forecast Offices and the NWS-NCEP provide dispersion model forecasts driven by NCEP Numerical Weather Prediction (NWP) models to emergency response managers. In addition, NCEP NWP predictions are made available to the Department of Homeland Security Inter-Agency Modeling and Atmospheric Assessment Center and the DOD Defense Threats Reduction Agency to drive their dispersion models. The atmospheric planetary boundary layer (PBL) height is a critical parameter for dispersion decision support tools. Accurate assessment of boundary layer information at finer scales should improve the Nation's ability to assess the effects of a toxic release. An ad-hoc PBL experiment was coordinated over the Washington, DC area during September 2009 to investigate the variability of the PBL over the urban area and to evaluate automated techniques to evaluate PBL height from regularly reporting radiosonde and aircraft profiles. The experiment was coordinated amongst various institutions and academia who brought special instruments to bear to evaluate the boundary layer. Ground based lidar measurements from NASA MPLNET, regular and special upper air profiles from Raobs and aircraft as well as CALIPSO satellite profiles were collected during the experiment. The NOAA Center for Atmospheric Science (NCAS) and University of Maryland, Baltimore County (UMBC) ground lidars and microwave radiometer measurements were analyzed to evaluate PBL variability, the automated PBL height method techniques and to serve to evaluate mesoscale model performance from NCEP and DOE/IMAAC facilities. These data are also used to evaluate a Real-Time Mesoscale Analysis (RTMA) of PBL height and are discussed by Tassone et al. at this conference. An overview of the experiment and results from the goals highlighted above will be presented.