US National Air Quality Forecast Capability: Progress toward initial implementation

NOAA is preparing to implement a National Air Quality Forecast Capability, per Congressional direction (1). The capability is being developed in partnership with the US EPA and state and local air quality forecasters. NOAA/National Weather Service's mesoscale weather prediction model (Eta) has been linked to the NOAA-EPA developed Community Multiscale Air Quality model to provide next-day forecast guidance, at hourly intervals, at the resolution of the Eta model (currently 12 km). Initially the guidance will provide predicted ground-level ozone concentrations, for a domain covering the Northeastern United States. Guidance will be issued twice daily on servers at NOAA and EPA. Development, testing and evaluation of the initial operational system began in 2003. Verification is based on EPA's real-time network of air quality monitoring compiled on the AIRNOW site. Real-time testing and evaluation of air quality forecast guidance produced from June through September, 2003 benefited from collaboration of a focus group of state and local air quality forecasters with developers, providing subjective feedback in addition to extensive diagnostic evaluation of utility, timeliness and accuracy. By August 2003, although the test capability was running reliably, with on-time delivery of twice-daily next-day forecast guidance and demonstrated achievement of minimal performance accuracy based on exceeding persistence forecasts, an overprediction bias, generally more pronounced at nighttime and over urban areas, had also emerged. Developmental testing feedback and diagnostic verification statistics were analyzed to identify causative factors for the bias and implement improvements in weather-air quality model linkage, vertical mixing, and ozone boundary conditions. These upgrades, and updated emissions information, will be incorporated in the experimental launch of air quality forecast guidance products, in June 2004, to provide the basis for operational deployment for the initial operational domain, scheduled for September, 2004. Contingent on successful testing and sufficient resources, the domain will be extended nationwide by 2009. Planned system upgrades, in addition to optimizing accuracy and performance, include extending the capability to airborne particulate matter and extending the forecast interval further in time.

The views expressed are those of the authors and do not necessarily represent those of the National Weather Service, NOAA or the EPA.

1) Energy Policy A Act of 2002; HR 4, SEC 1383