Grantee Research Project Results
2022 Progress Report: Automated model reduction for atmospheric chemical mechanisms
EPA Grant Number: R840013Title: Automated model reduction for atmospheric chemical mechanisms
Investigators: McNeill, V. Faye , Westervelt, Daniel , Henze, Daven , Fiore, Arlene M
Current Investigators: McNeill, V. Faye , Fiore, Arlene M , Westervelt, Daniel , Henze, Daven
Institution: Columbia University in the City of New York
EPA Project Officer: Chung, Serena
Project Period: August 1, 2020 through July 31, 2023 (Extended to July 31, 2025)
Project Period Covered by this Report: August 1, 2021 through July 31,2022
Project Amount: $799,699
RFA: Chemical Mechanisms to Address New Challenges in Air Quality Modeling (2019) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
To develop an automated mechanism reduction algorithm for generating high quality reduced isoprene mechanisms.
Progress Summary:
Since 2021, multiple methods of mechanism reduction have been evaluated, and a high accuracy reduced isoprene mechanism (AMORE-isoprene) has been produced through a combination of new algorithmic methods and manual adjustment.
The reduced isoprene mechanism that has been developed was tested and designed for use in the CMAQ modelling suiteand contains far fewer isoprene-based species (10) than the Caltech full mechanism (400) that it was based on. The development of this mechanism relied on a new algorithm designed specifically for the reduction of mechanisms by multiple orders of magnitude. This algorithm is a departure from earlier approaches to mechanism reduction and uses methods that are different from those described in the project proposal. In brief, the algorithm determines the essential set of connected pathways between isoprene and a small set of intermediate species which in turn are optimized to match the production of a set of important species of the full mechanism. The full methodology is described in our forthcoming paper currently in preprint.
The reduced mechanisms are converted to a F0AM readable format and input into Matlab. They are compared to the full mechanism they originated from to quantify their performance. An error metric was developed based on the difference in concentration of important species between the reduced and full mechanism. The error is averaged over multiple samples and species to determine an overall performance for the mechanism. This multi-sample multi-species error metric allows for the comparison of several different isoprene mechanisms. In our box model testing, the AMORE isoprene mechanism performs better than similarly sized isoprene mechanisms and similar to larger isoprene mechanisms.
The full mechanism used in this work was adapted from the complete isoprene mechanism published by Wennberg et al. at CalTech. This mechanism did not include complete chemical pathways for some species, however, these pathways were included in the CalTech reduced mechanism. An updated mechanism was created by extrapolating chemistry from the reduced Caltech mechanism into the full Caltech mechanism. This updated mechanism is the current working mechanism for reduction. Further testing needs to be done to confirm that this updated mechanism matches measured data.
Future Activities:
The project will continue on the same trajectory, employing various computational methods to develop algorithms for the reduction of chemical mechanisms. Multiple approaches are being developed, involving graph theory and genetic algorithms. Within the next reporting period, a complete algorithm will be developed for the automated reduction of generic chemical mechanisms that behave similarly to the isoprene mechanism.
We will be testing our published reduced mechanism in GEOS-Chem to provide more results demonstrating the utility of the mechanism. From this work, we will also develop a methodology for qualitative mechanism evaluation in GEOS-Chem.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 8 publications | 6 publications in selected types | All 6 journal articles |
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Wiser F, Place B, Sen S, Pye HOT, Yang B, Westervelt DM, Henze DK, Fiore AM, McNeill VF. AMORE-Isoprene v1.0:A new reduced mechanism for gas-phase isoprene oxidation. Geoscientific Model Development Discussions 2022;2022:1–30 |
R840013 (2022) |
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Supplemental Keywords:
Isoprene, mechanism reduction, atmospheric chemistry, secondary organic aerosol, graph theoryRelevant Websites:
MCNEILL GROUP @ COLUMBIA UNIVERSITY Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.