Daily Simulations of O3 and PM2.5 Over the Northeastern United States for Summer 2004 and Winter 2005: Assessing Model Performance, Seasonal Differences, and the Effects of Model Updates

This paper presents the application and assessment of a near-realtime air quality modeling system designed to simulate O3 and PM2.5 over the northeastern United States for summer 2004 and winter 2005. The air quality modeling system consists of operational weather forecasts from the National Weather Services (NWS) ETA model at a horizontal resolution of 12 km, the PREMAQ emissions and meteorology pre-processor, and the Community Multiscale Air Quality (CMAQ) model. The simulations were performed as a pilot study between the National Oceanic and Atmospheric Administration (NOAA), the U.S. Environmental Protection Agency (EPA), and the New York State Department of Environmental Conservation (NYSDEC) utilizing resources from the operational NWS/NOAA/EPA air quality forecasts. Results of our analysis indicate that the performance of the ETA/CMAQ modeling system for ozone simulations during the summer of 2004 is within the range of other numerical forecasting systems. Model performance for PM2.5 is compared between summer and winter simulations, utilizing both continuous total PM2.5 mass measurements and available speciation data. We also present an analysis of the sensitivity of PM2.5 predictions towards changes in CMAQ parameterizations, notably, an analysis of the sensitivity towards changing parameterization of turbulent vertical exchange. Finally, ETA/CMAQ simulations of O3 and PM2.5 for New York State are compared against predictions from other forecasting systems, including NYSDEC-issued operational air quality forecasts based on weather forecasts, climatology and expert judgment. Results for the summer of 2004 indicate that while both non-model based NYSDEC forecasts and ETA/CMAQ simulations clearly show better forecast skill than climatology and persistence for ozone, the picture is less clear for PM2.5 forecasts. This probably is indicative of the longer experience of NYSDEC forecasters with ozone predictions compared to PM2.5 predictions and the continued need to improve the state-of-science in simulating primary and secondary fine particulate matter in current-generation photochemical modeling systems.

DISCLAIMER Part of the research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW13921548. Although it has been reviewed by EPA, NOAA, and NYSDEC and approved for publication, it does not necessarily reflect their policies or views.