NOAA's Next-Generation Air Quality Predictions with the Unified Forecast System

NOAA’s next-generation regional air quality (AQ) prediction system and global aerosol predictions are being developed within the Unified Forecast System (UFS) framework to better forecast impacts of wildfire emissions on AQ in the United States (U.S.) as well as impacts of aerosols globally from hourly to seasonal time scales. The new regional UFS-AQM system consists of a new regional UFS weather model that is online coupled with chemistry represented by the EPA’s Community Multiscale AQ (CMAQ) modeling system with Carbon Bond VI and AERO6 mechanisms. Wildfire emissions are specified by the NESDIS Regional Hourly Advanced Baseline Imager (ABI) and Visible Infrared Imaging Radiometer Suite (VIIRS) Emissions (RAVE). Anthropogenic emissions are based on EPA’s National Emissions Inventories (NEI) over CONUS and global inventories elsewhere. Lateral boundary conditions for aerosols are provided by the Global Ensemble Forecast System with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) module (GEFS-Aerosols). UFS-AQM also includes a post-processing bias-correction procedure. Testing is performed over a large regional domain covering CONUS (and most of North America), Alaska and Hawaii. Testing and evaluation is underway in near-real time and for representative retrospective periods to evaluate readiness of UFS-AQM for potential operational implementation at the National Weather Service. Recent examples indicate substantially improved prediction with the new UFS-AQM of the impacts of wildfires on AQ, such as those from Quebec fires in the summer of 2023 on AQ in the Northeastern U.S., in comparison with the currently operational AQ prediction system.

Plans for further development of AQ predictions include higher spatial resolution consistent with the UFS Rapid Refresh Forecast System (RRFS), which is under development, and using aerosol lateral boundary conditions from a global 6-way coupled atmosphere - ocean - land - sea-ice - waves - aerosols UFS system, also under development. Data assimilation of fine particulate matter (PM2.5) observations from AirNow, VIIRS Aerosol Optical Depth (AOD) retrievals and TROPOspheric Monitoring Instrument (TROPOMI) NO2 retrievals into UFS-AQM is under development to constrain pollutant concentrations. Due to challenging computational requirements for UFS-AQM at high spatial resolution, a machine learning emulator is being developed to improve computational efficiency for prediction of chemical transformations and tracer transport.