Comparing RAMS And MM5 Prognostics For Use in CAMx Ozone Forecasting

Trend analyses point to an overall decrease in maximum ozone concentrations, but the frequency of peak ozone concentrations that exceed the National Ambient Air Quality Standard is rising. Health studies indicate that exposure to high ozone concentrations causes decreased functioning of mucous membranes and most clearly shows as a reduced capacity of the respiratory system particularly of children and older people. Recently emissions-based air quality prediction (AQP) systems have been implemented but are operating still on a research level. Driven by various meteorological forecast models the AQP systems provide prognostic fields for ozone predictions. Meteorological variables as temperatures, mixing heights, vertical diffusivity, are critical for appropriately predicting ozone concentrations. This study examines the sensitivity of an AQP forecast system to inputs from two prognostic meteorological models. We coupled the Comprehensive Air Quality Model with Extensions (CAMx) to the Meteorological Mesoscale Model (MM5 version 2) and the Regional Atmospheric Modeling System (RAMS version 4a). The AQS systems are run at 16 km grid resolution in a quasi-operational forecast mode. Ozone forecasts are provided for 24-hours for the Washington-Baltimore Metropolitan area. This study evaluates differences in predicted prognostic variables and their magnitude of impact on the accuracy of ozone forecasts.