Articles | Volume 18, issue 21
https://doi.org/10.5194/gmd-18-8461-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gmd-18-8461-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Model description paper
| 
13 Nov 2025
Model description paper |
| 13 Nov 2025
| 13 Nov 2025
The SAPRC atmospheric chemical mechanism generation system (MechGen)
William P. L. Carter
CORRESPONDING AUTHOR
College of Engineering Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, California 92521, USA
Jia Jiang
Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Zhizhao Wang
College of Engineering Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, California 92521, USA
Atmospheric Chemistry Observations & Modeling Lab, NSF National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80301, USA
Kelley C. Barsanti
Atmospheric Chemistry Observations & Modeling Lab, NSF National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80301, USA
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This paper describes the scientific basis for gas-phase atmospheric chemical mechanisms derived using the SAPRC mechanism generation system, MechGen. It can derive mechanisms for most organic compounds with C, H, O, or N atoms, including initial reactions of organics with OH, O3, NO3, and O3P or by photolysis, as well as the reactions of the various types of intermediates that are formed. The paper includes a description of areas of uncertainty where additional research and updates are needed.
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Chemical mechanisms describe the chemical processes in atmospheric models that are used to describe the changes in the atmospheric composition. Therefore, accurate chemical mechanisms are necessary to predict the evolution of air pollution and climate change. The article describes all steps that are needed to build chemical mechanisms and discusses the advances and needs of experimental and theoretical research activities needed to build reliable chemical mechanisms.
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Short summary
The SAPRC Atmospheric Chemical Mechanism Generation System (MechGen) generates explicit chemical reaction mechanisms for organic compounds. MechGen has been used for decades in the development of the widely used SAPRC mechanisms. This paper, detailing the software system, and a companion paper, detailing the chemical basis, represent the first complete documentation of MechGen. This paper includes examples and instructions for generating explicit and reduced mechanisms.
The SAPRC Atmospheric Chemical Mechanism Generation System (MechGen) generates explicit chemical...
