Progress on Configurable ATmospheric Chemistry (CATChem) within NOAA's Unified Forecast System (UFS)

The Unified Forecast System (UFS) is a community-based Earth system model that is designed to meet NOAA’s needs for atmospheric simulation and support its applications, not the least of which is the production of operational forecasts. Currently, the UFS can be configured to meet air composition forecast needs through the use of multiple chemistry components that range in complexity. Among these are NASA’s 2nd generation Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and the EPA Community Multiscale Air Quality (CMAQ) model. Because the multiple chemistry and chemistry-related processes are duplicated across different models within the UFS air composition structure, improvements in efficiency, structure, and ease of code maintenance can be realized through improvements in its interface.

Through collaborative efforts between multiple NOAA laboratories and cooperative institute partners, the Configurable ATmospheric Chemistry (CATChem) component of the UFS will include all of the chemical and aerosol processes necessary to produce atmospheric chemistry and air composition simulations within the UFS framework. This goal will be accomplished through the development of a flexible, easy-to-modify, and well-documented infrastructure. Innovative research capabilities that improve gas-phase chemistry and aerosol processes will be added. Examples include options to use gas-phase chemical mechanisms and aerosol schemes of varying complexity, the ability to couple different chemical mechanisms with different physics options easily, and improvements in the flexibility of emissions processing. The improved flexibility of CATChem will make the UFS applicable for both research and operational needs within the unified chemistry component. These improvements in interface will further engage the atmospheric chemistry research community and promote the efficient and prompt advance of research within the UFS and research to operations (R2O) transitions – all of which are critical to ensure state-of-the-science air quality and air composition forecasts.

CATChem is freely available from the UFS-Community GitHub page, https://github.com/ufs-community/CATChem.