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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: model evaluation paper 27 Oct 2020

Submitted as: model evaluation paper | 27 Oct 2020

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This preprint is currently under review for the journal GMD.

The Community Multiscale Air Quality (CMAQ) Model Versions 5.3 and 5.3.1: System Updates and Evaluation

K. Wyat Appel1, Jesse O. Bash1, Kathleen M. Fahey1, Kristen M. Foley1, Robert C. Gilliam1, Christian Hogrefe1, William T. Hutzell1, Daiwen Kang1, Rohit Mathur1, Benjamin N. Murphy1, Sergey L. Napelenok1, Christopher G. Nolte1, Jonathan E. Pleim1, George A. Pouliot1, Havala O. T. Pye1, Limei Ran1,a, Shawn J. Roselle1,, Golam Sarwar1, Donna B. Schwede1, Fahim I. Sidi1, Tanya L. Spero1, and David C. Wong1 K. Wyat Appel et al.
  • 1Center for Environmental Measurement and Modeling, Office of Research and Development, U.S. Environmental Protection Agency, RTP, NC, USA
  • anow at: Natural Resources Conservation Service, U.S. Department of Agriculture, Greensboro, NC, USA
  • retired

Abstract. The Community Multiscale Air Quality (CMAQ) model version 5.3 (CMAQ53), released to the public in August 2019 and followed by version 5.3.1 (CMAQ531) in December 2019, contains numerous science updates, enhanced functionality, and improved computation efficiency relative to the previous version of the model, 5.2.1 (CMAQ521). Major science advances in the new model include a new aerosol module (AERO7) with significant updates to secondary organic aerosol (SOA) chemistry; updated chlorine chemistry; updated detailed bromine/iodine chemistry; updated simple halogen chemistry; addition of dimethyl sulfide (DMS) chemistry in the CB6r3 chemical mechanism; updated M3Dry bi-directional deposition model; and the new Surface Tiled Aerosol and Gaseous Exchange (STAGE) bi-directional deposition model. In addition, support for the Weather Research and Forecasting (WRF) model’s hybrid vertical coordinate (HVC) system was added to CMAQ53 and the Meteorology-Chemistry Interface Processor (MCIP) version 5.0 (MCIP50). Enhanced functionality in CMAQ53 includes the new Detailed Emissions Scaling, Isolation and Diagnostic (DESID) system for scaling incoming emissions to CMAQ and reading multiple gridded input emission files.

Evaluation of CMAQ53 was performed by comparing monthly and seasonal mean daily 8-hr average (MDA8) O3 and PM2.5 values from several CMAQ531 simulations to a similarly configured CMAQ521 simulation encompassing 2016. For MDA8 O3, CMAQ531 has higher O3 in the winter versus CMAQ521, due primarily to reduced dry deposition to snow, which strongly reduces wintertime O3 bias. MDA8 O3 is lower with CMAQ531 throughout the rest of the year, particularly in spring, due in part to reduced O3 from the lateral boundary conditions (BCs), which generally increases MDA8 O3 bias in spring and fall. For daily 24-hr average PM2.5, CMAQ531 has lower concentrations on average in spring and fall, higher concentrations in summer, and similar concentrations in winter as CMAQ521, which slightly increases bias in spring and fall and reduces bias in summer. Comparisons isolating updates to several specific aspects of the modeling system, namely the lateral BCs, meteorology model version, and the deposition model used, were also performed. Transitioning from a hemispheric CMAQ (HCMAQ) version 5.2.1 simulation to a HCMAQ version 5.3 simulation to provide lateral BCs contributes to higher O3 mixing ratios in the regional CMAQ simulation in higher latitudes during winter (due to the decreased O3 dry deposition to snow in CMAQ53) and lower O3 mixing ratios in mid and lower latitudes year-round (due to reduced O3 over the ocean with CMAQ53). Transitioning from WRF version 3.8 to WRF version 4.1.1 with the HVC system resulted in consistently higher (1.0–1.5 ppbv) MDA8 O3 mixing ratios and higher PM2.5 concentrations (0.1–0.25 µg m−3) throughout the year. Finally, comparisons of the M3Dry and STAGE deposition models showed that MDA8 O3 is generally higher with M3Dry outside of summer, while PM2.5 is consistently higher with STAGE due to differences in the assumptions of particle deposition velocities to some surfaces between the two models. For ambient NH3, STAGE has slightly higher concentrations and smaller bias in the winter, spring, and fall, while M3Dry has higher concentrations and smaller bias, but larger error and lower correlation, in the summer.

K. Wyat Appel et al.

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Status: open (until 22 Dec 2020)
Status: open (until 22 Dec 2020)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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K. Wyat Appel et al.

Model code and software

CMAQ version 5.3 United States Environmental Protection Agency

CMAQ version 5.3.1 Unites States Environmental Protection Agency

K. Wyat Appel et al.


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Latest update: 01 Dec 2020
Publications Copernicus
Short summary
This paper details the scientific updates in the recently released CMAQ version 5.3 (and v5.3.1), and also includes operational and diagnostic evaluations of CMAQv5.3.1 against observations and the previous version of the CMAQ (v5.2.1). This work was done to improve the underlying science in CMAQ. This article is used to inform the CMAQ modeling community of the updates to the modeling system and the expected change in model performance from these updates (versus the previous model version).
This paper details the scientific updates in the recently released CMAQ version 5.3 (and...