Linking the Eta Model with the Community Multiscale Air Quality (CMAQ) Modeling System to Build a National Air Quality Forecasting System

TLDR

NOAA and the EPA have created a national air quality forecasting system that uses the NCEP Eta Model and EPA’s CMAQ to generate gridded ozone forecasts, providing the first nationwide guidance—especially for rural areas—helping forecasters predict and alert the public to poor air quality. The paper aims to describe the linkage of the Eta Model and CMAQ for a national AQF system and outline plans to expand its coverage, particle forecasting, and forecast horizon. The system, operational since September 2004, produces twice‑daily 12‑km ozone forecasts for the northeastern United States by coupling the NCEP Eta Model with the EPA CMAQ, and the paper details the software components, technical and logistical considerations of this linkage. Pre‑operational testing during the 2003 and 2004 ozone forecast seasons demonstrated that the AQF system offered valuable guidance for air quality forecasters.

Abstract

Abstract NOAA and the U.S. Environmental Protection Agency (EPA) have developed a national air quality forecasting (AQF) system that is based on numerical models for meteorology, emissions, and chemistry. The AQF system generates gridded model forecasts of ground-level ozone (O3) that can help air quality forecasters to predict and alert the public of the onset, severity, and duration of poor air quality conditions. Although AQF efforts have existed in metropolitan centers for many years, this AQF system provides a national numerical guidance product and the first-ever air quality forecasts for many (predominantly rural) areas of the United States. The AQF system is currently based on NCEP’s Eta Model and the EPA’s Community Multiscale Air Quality (CMAQ) modeling system. The AQF system, which was implemented into operations at the National Weather Service in September of 2004, currently generates twice-daily forecasts of O3 for the northeastern United States at 12-km horizontal grid spacing. Preoperational testing to support the 2003 and 2004 O3 forecast seasons showed that the AQF system provided valuable guidance that could be used in the air quality forecast process. The AQF system will be expanded over the next several years to include a nationwide domain, a capability for forecasting fine particle pollution, and a longer forecast period. State and local agencies will now issue air quality forecasts that are based, in part, on guidance from the AQF system. This note describes the process and software components used to link the Eta Model and CMAQ for the national AQF system, discusses several technical and logistical issues that were considered, and provides examples of O3 forecasts from the AQF system.