Impact of Cloud Parameters on NOAA’s NAQFC Surface Ozone Predictions: Evaluations and Sensitivity Studies

The National Air Quality Forecasting Capability (NAQFC) was upgraded with the latest version of NOAA Non-hydrostatic Multiscale Model with Arakawa B grid-staggering (NMMB) and the EPA Community Multiscale Air Quality (CMAQ) model v5.0.2 in June 2017. With these model upgrades, the forecast skill scores for surface ozone predictions were improved. However, several ozone exceedance events were missed during the 2017 ozone season by the upgraded NAQFC predictions. Derived cloud parameters recalculated within CMAQ pre-processor (named as PREMAQ), are considered to be one of the culprits responsible for under-predictions of surface ozone due to their impacts on photolysis rates. In this study, the PREMAQ-calculated cloud covers are evaluated with the available satellite measurements and observational data through the Model Evaluation Tools (MET). Two sensitivity runs are performed, where the NAM-predicted and NAM nest–predicted cloud variables are directly used in the CMAQ simulations. The sensitivity-run results will be compared with the current operational forecasts and will be evaluated with various observational data. Recommendations will be provided to improve surface ozone predictions for the future implementation based on findings from this study.