Evaluation of the MPAS-CMAQ Global Air Quality Modeling System

A next generation air quality modeling system is being developed at the U.S. EPA to enable modeling of air quality from global to regional to local scales. The system will have three configurations: 1. Global meteorology with seamless mesh refinement and online (coupled) atmospheric chemistry; 2. Regional (limited area) online meteorology and chemistry; and 3. Offline (sequential) regional meteorology and chemistry. We have developed a global online configuration which includes the Model for Prediction Across Scales – Atmosphere (MPAS-A), developed at the National Center for Atmospheric Research (NCAR), coupled with the latest version of the Community Multiscale Air Quality (CMAQv5.3) model developed at the U.S. EPA.

In this presentation we will present the initial evaluation of air quality model simulations by the MPAS-CMAQ system for the full year of 2016 using a mesh with 92 km global resolution refining to 25 km over North America. Global emissions from EDGAR-HTAP are combined with the 2016 EPA National Emission Inventory for the US. Evaluation of meteorology simulated by the EPA-enhanced version of MPAS-A that includes the addition of four-dimensional data assimilation (FDDA), the ACM2 PBL model, and PX land surface model will be presented in another talk. This presentation will focus on global and US evaluations of concentrations and deposition of air quality constituents. Evaluation includes comparisons to gas and aerosol surface-based measurement networks in the US and other regions of the world. In addition, we compare to global satellite data such as MODIS AOD and OMI NO₂. Our technique of assimilating ozone concentrations from GFS analyses for layers above the tropopause is evaluated through comparisons to the WOUDC global ozonesonde network.