An Operational Evaluation of ETA-CMAQ Air Quality Forecast Model

The National Oceanic and Atmospheric Administration (NOAA), in cooperation with the Environmental Protection Agency, is developing an Air Quality Forecasting Program that will eventually result in an operational Nationwide Air Quality Forecasting System. The initial phase of this program, which couples NOAA’s Eta meteorological model with EPA’s Community Multiscale Air Quality (CMAQ) model, began operation since May of this year and has been providing forecasts of hourly ozone concentrations over the northeastern United States. As part of this initial phase, an evaluation of the coupled modeling system has been performed in which both discrete forecasts (observed versus modeled concentrations) for hourly, maximum 1-hr, and maximum 8-hr O3 concentrations and categorical forecasts (observed versus modeled exceedances / non-exceedances) for both the maximum 1-hr (125 ppb) and 8-hr (85 ppb) were evaluated. The evaluation encompasses one month (1 June – 30 June, 2004) and uses hourly O3 concentration measurements from the EPA’s AIRNOW network.