WRF-Chem and WRF Configuration and Specifics

The NCAR near-real-time regional air quality forecasts over the contiguous United States (CONUS) has been developed for a multitude of objectives which include supporting community model development, allowing early identification of model errors and biases, supporting the atmospheric science community in their research, and assisting field campaign planning (e.g.  FIREX-AQ 2019, AEROMMA 2023 ) and air quality decision-making. The forecasts are an experimental research project and aim to complement the operational air quality forecasts produced by the National Oceanic and Atmospheric Administration (NOAA). The forecasting system is based on the Weather Research and Forecasting model with Chemistry (WRF-Chem). 

Original setup (June 2019 - December 2023) “firex-aq”

Daily 48-h forecast at 12 km x 12 km grid spacing over CONUS using the MOZCART chemical mechanisms, hourly NEI2014v2 emissions (monthly averages), FINNv1 fire emissions, MEGAN online biogenic emissions, carbon monoxide tracers and inert tracers for various sources. WRF-Chemv3.9.1. See FIREX-AQ Tracers for more information. 

AQ-WATCH Setup (June 2020-December 2023) - “aq-watch”

Parallel forecasts setup for the European Union project AQ-WATCH. Based on the original setup but with the following changes:  Nested domain (12 km x 12 km CONUS, 4 km x 4 km Colorado), T1-MOZCART chemical mechanism, trend adjusted hourly day-specific NEI2017v2 emissions, FINNv1 fire emissions with double aerosol emissions and MEGAN biogenic emissions with isoprene scaled to 50%.  WRF-Chemv4.1. 

WRF-only high resolution forecast (March 2022-December 2023)

Meteorological variables at a 1.3 km x 1.3 km resolution over the greater Northern Colorado Front Range. WRFv4.1.

CONUS-AQ (29 December 2023 - present)

• 3-domains: 
  • WRF-Chemv4.1 (T1-MOZCART): 12 km x 12 km CONUS (d01) and 4 km x 4 km Colorado (d02)
  • WRFv4.1 (met-only): 1.3 km x 1.3 km greater Northern Colorado Front Range (d03) 
• Emissions: 
  • FINNv2.5 fire emissions, MEGAN biogenic emissions
  • d01: trend adjusted hourly day-specific NEI2017v2 emissions
  • d02: hourly day-specific NEI2014v2 emissions
• Other namelist settings as listed at FIREX-AQ Tracers.

Visualizations and NRT evaluations 

• Hourly forecast maps of key chemical and meteorological variables ➩
  Until December 2023 variables names without domain suffix refer to “firex-aq”, d01 and d02 refer to “aq_watch” and d03 to the WRF-only setup. Starting January 2023 variable names without suffix refer to the CONUS-AQ 12 km domain and d02 and d03 to the 4km and 1.3 km domains. 
• MELODIES MONET NRT evaluation with surface ozone and PM2.5 ➩
  (firex-aq d01 setup up to December 2023, CONUS-AQ d01 and d02 afterwards)
• Forecasts for and Comparison with TOLNET (d01) ➩
  (firex-aq d01 setup up to December 2023, CONUS-AQ d01 afterwards)
• Comparison with WRFTropOmi NO2 (d01) ➩
  (firex-aq d01 setup up to December 2023, CONUS-AQ d01 afterwards)

Forecast Evaluation Publications

• Kumar R, Bhardwaj P, Pfister G, Drews C, Honomichl S, D’Attilo G. Description and Evaluation of the Fine Particulate Matter Forecasts in the NCAR Regional Air Quality Forecasting System. Atmosphere. 2021; 12(3):302. https://doi.org/10.3390/atmos12030302
• Chouza, F., Leblanc, T., Brewer, M., Wang, P., Piazzolla, S., Pfister, G., Kumar, R., Drews, C., Tilmes, S., Emmons, L., and Johnson, M. 2021: The impact of Los Angeles Basin pollution and stratospheric intrusions on the surrounding San Gabriel Mountains as seen by surface measurements, lidar, and numerical models, Atmos. Chem. Phys., 21, 6129–6153, https://doi.org/10.5194/acp-21-6129-2021.
• Evaluation and Application of the NCAR CONUS Air Quality Research Forecasting System, presented at MAC-MAQ 2023

Data Access

We invite the community to use our forecasting products for their research, as input for urban scale air quality simulations, or for the co-development of customized products. Raw model data can be accessed through the NCAR RDA.

Last updated: January 2024