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Evaluation of air quality modeling from EQUATES: EPA’s Air Quality Time Series Project
Citation:
Foley, K., C. Hogrefe, Keith Appel, R. Gilliam, G. Pouliot, AND S. Benish. Evaluation of air quality modeling from EQUATES: EPA’s Air Quality Time Series Project. International Technical Meeting on Air Pollution Modeling and its Application, Chapel Hill, NC, May 22 - 26, 2023.
Impact/Purpose:
EPA’s Air QUAlity TimE Series Project (EQUATES; www.epa.gov/cmaq/EQUATES) uses the state-of-the-science emissions, meteorological, and air quality methods and models to provide a unified set of modeling data for 2002-2017 to support regulatory and policy analyses as well as health and ecological studies. Modeled datasets cover the Conterminous US at a 12km resolution and the northern hemisphere at a 108km resolution using the Community Multiscale Air Quality modeling system version 5.3.2 (CMAQv5.3.2; https://www.epa.gov/CMAQ). New hemispheric and North American emissions inventories were developed using, to the extent possible, consistent input data and methods across all years, including emissions from mobile, fire, and oil and gas sources. The new emissions datasets and CMAQ output have been made publicly available to support a wide variety of human health and ecological applications. For example, modeled deposition will be used by the National Atmospheric Deposition Program (NADP) Total Deposition Science Committee (TDEP) to estimate total sulfur and nitrogen deposition for use in critical loads and other ecological assessments. Model estimated trends will be used for dynamic and diagnostic evaluation of the CMAQ system to inform model development and build confidence in the use of the model for quantifying the impact of meteorological and emissions changes on air quality.
Description:
The EPA’s Air QUAlity TimE Series Project (EQUATES) includes a set of modeled meteorology, emissions, air quality, and pollutant depositions spanning the years 2002 through 2019. Modeled datasets cover the Conterminous US with 12-km horizontal grid spacing and the Northern Hemisphere with a 108-km spacing. Decadal air quality estimates from the Community Multiscale Air Quality (CMAQ) model for the US from EQUATES are compared to trends from previous long-term CMAQ simulations and to observational data. Diurnal and seasonal patterns in PM2.5 are substantially improved in EQUATES across most of the country compared to previous CMAQ modeling. Decreasing trends in peak ozone in the eastern US are captured by the model, however a flattening of these trends in the observed values starting around 2015 is not reflected in model values. In addition, both ozone and PM2.5 are underestimated at many sites in the western US. We explore possible causes for model bias across seasons, regions, and species. We will also highlight EQUATES datasets that are publicly available and can be used to support a wide variety of human health and ecological modeling applications as well as model evaluation and development.