Impact of meteorological model resolution on PBL height errors

Boundary layer depth (PBL) is a key parameter in air quality modeling determining extent of turbulence and dispersion for pollutants. NOAA/NWS/NCEP has developed a near real-time PBL height verification system to help evaluate the contribution of meteorological model error to air quality model errors. Currently, PBL depths from the NOAA/NWS National Centers for Environmental Prediction (NCEP) North American Model NAM (WRF/NMM) are verified with boundary layer heights derived from NWS radiosonde data and aircraft observations reported by Aircraft Communications Addressing and Reporting System (ACARS). The Richardson number approach is applied to radiosonde and ACARS profiles of winds, temperature and moisture (when available) to determine and evaluate the observed PBL depth. ACARS estimates allow for the diurnal estimate of boundary layer development and collapse which are not possible from typical NWS radiosondes. This paper will summarize recent improvements to the NCEP boundary layer verification system. In addition, the NAM PBL depths for two varying horizontal resolutions (12km and 4km) will be verified against ACARS and radiosonde estimates. Regional statistics (e.g.: Inland versus coastal areas), as well as comparison for individual stations (e.g.: urban vs rural sites) will be demonstrated. Finally PBL height errors along with other meteorological parameters errors are compared to the NOAA NAM – Community Model for Air Quality (CMAQ) AQF (Air Quality Forecast) system predictions for poor air quality episodes. These comparisons will help to quantify the impact of meteorological model performance on air quality forecast errors.