Submitted as: development and technical paper
06 Oct 2022
Submitted as: development and technical paper | 06 Oct 2022
Status: a revised version of this preprint is currently under review for the journal GMD.

AMORE-Isoprene v1.0: A new reduced mechanism for gas-phase isoprene oxidation

Forwood Wiser1, Bryan Place2, Siddhartha Sen3, Havala O. T. Pye4, Benjamin Yang5,9, Daniel M. Westervelt5,6, Daven K. Henze7, Arlene M. Fiore8,9, and V. Faye McNeill1,9 Forwood Wiser et al.
  • 1Department of Chemical Engineering, Columbia University, New York, NY USA 10027
  • 2ORISE Fellow at the Office of Research and Development, Environmental Protection Agency, Research Triangle Park, NC, USA 27711
  • 3Microsoft Research, New York, NY, USA 10012
  • 4Office of Research and Development, Environmental Protection Agency, Research Triangle Park, NC, USA 27711
  • 5Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA 10964
  • 6NASA Goddard Institute for Space Studies, New York, NY, 10025
  • 7Department of Mechanical Engineering, University of Colorado, Boulder, Boulder, CO, USA 80309
  • 8Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA USA 02139
  • 9Department of Earth and Environmental Sciences, Columbia University, New York, NY USA 10027

Abstract. Gas-phase oxidation of isoprene by ozone (O3) and the hydroxyl (OH) and nitrate (NO3) radicals significantly impacts tropospheric oxidant levels and secondary organic aerosol formation. The most comprehensive and up to date chemical mechanism for isoprene oxidation consists of several hundred species and over 800 reactions. Therefore, the computational expense of including the entire mechanism in large-scale atmospheric chemical transport models is usually prohibitive, and most models employ reduced isoprene mechanisms ranging in size from ∼10 to ∼200 species. We have developed a new reduced isoprene oxidation mechanism using a directed graph path-based automated model reduction approach, with minimal manual adjustment of the output mechanism. The approach takes as inputs a full isoprene oxidation mechanism, the environmental parameter space, and a list of priority species which are protected from elimination during the reduction process. Our reduced mechanism, AMORE-Isoprene, consists of 12 species which are unique to the isoprene mechanism and 22 reactions. We demonstrate its performance in a box model in comparison with experimental data from the literature and other current isoprene oxidation mechanisms. AMORE-Isoprene’s performance for predicting the time evolution of isoprene oxidation products, including isoprene epoxydiols (IEPOX) and formaldehyde, is favorable compared to other similarly sized mechanisms. When AMORE-Isoprene is included in the Community Regional Atmospheric Chemistry Multiphase Mechanism 1.0 (CRACMM1AMORE) in CMAQ v5.3.3, O3 and formaldehyde agreement with EPA Air Quality System observations are improved. O3 bias is reduced by 3.4 pbb under daytime conditions for O3 concentrations over 50 ppb. Formaldehyde bias is reduced by 0.26 ppb on average for all formaldehyde measurements compared to the base CRACMM1. There was no significant change in computation time between CRACMM1AMORE and the base CRACMM. AMORE-Isoprene shows a 35 % improvement in agreement between simulated IEPOX concentrations and chamber data over the base CRACMM1 mechanism when compared in the F0AM box model framework. This work demonstrates the potential value of automated model reduction for complex reaction systems.

Forwood Wiser et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2022-240', Anonymous Referee #1, 21 Nov 2022
  • RC2: 'Comment on gmd-2022-240', Anonymous Referee #2, 20 Dec 2022
  • AC1: 'Response to reviewers', V. Faye McNeill, 31 Jan 2023

Forwood Wiser et al.

Model code and software

Code and data for the AMORE algorithm Forwood Wiser

Forwood Wiser et al.


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Short summary
We developed an automated method, AMORE, to simplify complex chemical mechanisms. We applied AMORE to the oxidation mechanism for isoprene, an abundant biogenic volatile organic compound. Using AMORE with minimal manual adjustments to the output, we created the AMORE-isoprene mechanism, with improved accuracy and similar size to other reduced isoprene mechanisms. AMORE-Isoprene improved the accuracy of EPA’s CMAQ model compared to observations.