Users Manual for the SAPRC Atmospheric Chemical Mechanism Generation System

Overview of MechGenMechGen is a computer program designed to derive fully explicit mechanisms for the reactions of a wide range of emitted organic compounds and their oxidation products as they react in the atmosphere. These reactions occur in the presence of oxides of nitrogen and other pollutants. Additionally, the program can optionally derive lumped mechanisms that are suitable for atmospheric models. The scientific methodology behind how chemical reactions and rate constants are derived or estimated is detailed in a separate paper (Carter et al., 2024). A paper discussing the algorithms and test cases is currently in preparation. MechGen is publicly accessible through both a web-based and terminal-based interface. It can be used to generate explicit mechanisms for individual compounds, as well as to access associated documentation. A Telnet login provides access to advanced features such as deriving mechanisms for multiple compounds, multi-generation mechanisms, and portions of lumped mechanisms for airshed models. This interface also allows users to program and manage the system. Document Scope This document explains: How to access and use the online system to generate explicit and lumped mechanisms, including mechanisms with user-defined lumping and explicit reaction assignments. How to obtain and install a local copy of the software for advanced features, such as: Deriving multi-generation mechanisms. Developing new lumping methods. Using these methods to create lumped atmospheric reaction mechanisms for airshed models.