Evaluation of PBL depths for poor air quality episodes from the NOAA forecast systems

Boundary layer depth is a key parameter in air quality modeling determining extent of turbulence and dispersion for pollutants. Boundary layer depths from several model systems operating at NOAA/NWS National Centers for Environmental Prediction (NCEP) – North American Model NAM (WRF/NMM), newly developed NOAA environmental modeling system (NEMS/NMMB) and Community Model for Air Quality (CMAQ) - are verified with the observations received from the Aircraft Communications Addressing and Reporting System (ACARS) and radiosonde (RAOBS). To determine PBL depth from the observations, Richardson number approach is applied. Overall statistics including diurnal cycle and time series for different models and different resolutions (12 km and 4 km for the NMMB model) are analyzed with an emphasis on the impact of resolution on predicting boundary layer depth. PBL depths for poor air quality episodes are examined and compared to ozone forecasts provided by NOAA AQ Forecast System. The August 17, 2009 high ozone episode is studied, as well as several other episodes during August 2010. Other meteorological parameters (temperature, wind, humidity, cloud cover) are analyzed to determine their impact on ozone forecast. Also, boundary layer depths from other NCEP models - Rapid Update Cycle (RUC), Short-range ensemble forecast (SREF) and Global Forecast System (GFS) - are verified.