Evaluation of FV3 for Use with Air Quality Applications

Operational air quality predictions for the United States (U. S.) are provided from NOAA by the National Air Quality Forecasting Capability (NAQFC). NAQFC provides nationwide operational predictions of ozone and particulate matter. Predictions are produced twice per day (at 06 and 12 UTC cycles) at 12 km resolution and 1 hour time intervals through 48 hours and distributed at http://airquality.weather.gov. The NOAA National Centers for Environmental Prediction (NCEP) operational North American Mesoscale (NAM) 12 km weather forecast system is used to drive the Community Multiscale Air Quality (CMAQ) model. Recently, NCEP, along with other NOAA labs and research communities, has developed the Next Generation Global Prediction System (NGGPS) based on the Finite Volume Cubed Sphere core FV3 dynamical core as it moves towards a Unified Forecasting System (UFS). The FV3-GFS (GFSv15) is run at similar resolution (13 km) to the NAM while mainly using the standard NCEP global model (GFSv14) physics. Simple aerosol chemistry is also being incorporated into GFSv15 and is designed to replace the NCEP operational NEMS Global Aerosol Capability (NGAC) that uses GFSv14. The transition to the FV3 dynamic core should allow for unification of regional and global atmospheric composition predictions models and one step in this process is to see if CMAQ can perform as well with meteorological forcing from GFSv15 as it does with forcing from the NAM. This study evaluates the ability of the GFSv15 and to predict boundary layer processes important for driving air quality prediction as compared to the operational NAM. A stand-alone regional (SAR) version of GFSv15 is used and applied for selected air quality episodes over the CONUS.

The boundary layer mixing schemes used by NAM and GFSv15 employ very different mechanisms (eg: local vs non-local vertical mixing) that could have important impacts on air quality prediction. The weather models will be evaluated for both summer and winter against standard and mesonet fields averaged for various regions with emphasis on the evaluation of meteorological fields important to prediction of ozone and fine particulate matter (eg: near surface winds, temperatures, moisture and boundary layer heights, cloud cover). Finally, a comparison of CMAQ model performance using NAM and GFSv15 – SAR meteorological predictions will be presented.