Breathing Better: On NOAA’s Air Resources Laboratory Continuous Development of the National Air Quality Forecasting Capability

Since its establishment two decades ago, the National Air Quality Forecasting Capability (NAQFC) has provided real-time air quality forecasts for the United States (https://www.weather.gov/sti/stimodeling_airquality_predictions). NOAA’s Air Resources Laboratory (ARL) has been pivotal in the development and improvement of the NAQFC, which consequently has improved the health and lives of Americans, while saving billions of dollars each year. The NAQFC has historically and continues to use the U.S. EPA’s Community Multiscale Air Quality (CMAQ) model for its chemical composition predictions, while its meteorological model drivers have changed from the Eta, WRF-NMM, NMM-B, and FV3GFS over this time. To facilitate the use of these operational meteorological data, preprocessors such as “PreMAQ” and the NOAA-EPA Atmosphere-Chemistry Coupler (NACC) were developed at ARL. To ensure acceptable air quality model predictions and performance, research and development has been performed on such aspects as the planetary boundary layer height, eddy diffusivities, and other important meteorological and surface parameter drivers for the NAQFC

Emissions are a crucial input to the NAQFC’s air quality predictions. In addition to continuously updating, adjusting, and evaluating anthropogenic emissions in the NAQFC from the U.S. EPA’s National Emission Inventory (NEI), NOAA/ARL has also developed novel intermittent, process-based models such as the FENGSHA windblown dust model, and near-real-time biomass burning emissions using the NOAA Hazard Mapping System (HMS)/BlueSky pipeline, as well as top-down, satellite-retrieved fire radiative power (FRP) techniques. In the upcoming implementation of NOAA’s next-generation, Unified Forecast System (UFS) Air Quality Model (AQM) component for the NAQFC, NOAA-ARL has adapted a new emission modeling system based on the Harmonized Emissions Component (HEMCO), known as NOAA’s Emission and Exchange Unified System (NEXUS). Future NAQFC implementations are expected to update multiple aspects of air-surface exchange processes (for both emissions and deposition), including novel multi-layer vegetative canopy effects and improved chemical data assimilation. NOAA-ARL has also been heavily involved in research and development in constraining the important chemical lateral boundary conditions (CLBC) for the NAQFC’s regional domains in the U.S., through the use of data from global models and chemical initial conditions (CIC) adjusted via chemical data assimilation. To verify the current and future NAQFC predictions, NOAA-ARL developed the Model and ObservatioN Evaluation Toolkit (MONET), which is an open source project and Python package that aims to create a common platform for atmospheric composition data analysis for weather and air quality models.

Over the past 20 years, NOAA-ARL has contributed to nearly every component of the NAQFC, and has successfully been able to balance the need for continuous scientific advancements, acceptable model performance, and community-available products. It is anticipated that NOAA-ARL will continue to expand NOAA's atmospheric composition models beyond regional air quality, encompassing global/chemical reanalysis, air-surface exchange processes, weather-chemical feedback, and more.