ACM Training & Panel

ACM Training & Panel Discussion

The training "Current Atmospheric Chemical Mechanisms" and a follow up panel discussion "The Future of Atmospheric Chemical Mechanisms Development: A discussion of Possible Forward Paths" was offered to the public before the bi-annual ACM Conference. A summary of both sessions can be found below. For those that were unable to join us live, the training and discussion was recorded for you to review and to share widely with colleagues. 

If you have not yet watched the training, you should do so before providing comment.

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If you have not yet watched the panel discussion, you should do so before providing comment.

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A summary of the questions asked during the sessions has been developed and the technical program committee welcomes additional input from other academics and researchers. You can view the original summary document below and then if you have a follow up question, please send it directly to the researcher you are asking to ensure a prompt response. 

Original Discussion Document     

Thursday, November 5th

8:00 a.m. PT - 11:00 a.m. PT

Current Atmospheric Chemical Mechanisms Training

Training Topics: 


This training will start with an overview of the Master Chemical Mechanism (MCM) by Dr. Andrew Rickard, University of York. He will discuss its origins, philosophy, applications and future development strategy.  Then Dr. Bill Carter, UC Riverside, will describe the history, objectives, and approach used in the development of the SAPRC mechanisms and the SAPRC mechanism generation system (MechGen) and their current status and plans. The approach used is an example of that advocated in the "New Directions" article of Kaduwela et al (2016). Next, Dr. William Stockwell, University of Texas at El Paso, will discuss RADM/RACM/GACM Mechanisms. The Regional Acid Deposition Mechanism (versions 1 and 2) and the Regional Atmospheric Chemistry Mechanism (versions 1 and 2) constitute a mechanism series designed for 3-D photochemical grid models. The design philosophy of this series is to balance completeness, compactness and the necessary speculations that are needed to make air quality models that are creditable for policymakers. Dr. Wendy Goliff, Riverside City College, will continue the discussion on RACM2 because chemical mechanisms are an important bridge between laboratory data and modeling.  Finally, Dr. Greg Yarwood, Ramboll, will review the development of Carbon Bond (CB) mechanisms leading to the current version, namely revision 5 of CB6 (CB6r5). He will discuss a formal uncertainty analysis of CB6r4 that considers the impact of uncertainty in each rate constant and product stoichiometric coefficient of this mechanism.

Friday, November 6th

8:00 a.m. PT - 10:00 a.m. PT

The Future of Atmospheric Chemical Mechanism Development: A Panel Discussion of Possible Forward Paths



Kaduwela et al. (2015) and Stockwell et al. (2020) present two differing views on the further development of gas-phase atmospheric chemical mechanisms. Kaduwela et al. call for the reliance on master chemical mechanisms, that are as complete as possible, to develop reduced chemical schemes for air quality modeling for public policy development.  It is argued that this approach provides direct links between fundamental chemistry and air quality modeling applications. This view places a strong emphasis on examining all non-negligible chemical reaction paths. 

Stockwell et al. recognize that master chemical mechanisms are worthy research endeavors. But they are concerned that reliance on the creation of a very large, explicit mechanism as the first step may involve an extensive extrapolation of SAR data that may go too far beyond the available experimental database. They are concerned that the master mechanism approach may introduce greater uncertainty into public policy modeling. Methods based on data mining, machine learning, data assimilation or similar mathematical approaches may provide the policy community with more reliable modeling tools.

Both Kaduwela et al. and Stockwell et al. agree that expanding the available chemical database, including laboratory, chamber and field data, are extremely important to the development of future atmospheric chemistry mechanisms.

This panel discussion will follow on the background provided in the descriptions of various current mechanism development efforts on the previous day, but will focus specifically on the differing views on the future of mechanism development. We intend this to be a discussion and not a debate. The panel will consist of several current mechanism developers and will include short opening statements from each perspective. Following that, there will be a discussion between the panelists and the audience. We will clearly delineate the specific areas of agreement, disagreement and possible forward paths for the mechanism development community.