EOMF-02. Capabilities of NOAA's global chemical forecast systems: GEFS-Aerosols, UFS-Aerosols, and UFS-Chem

Abstract
There are three global chemical forecast systems in operation and under development at NOAA National Weather Service (NWS) and Oceanic and Atmospheric Research (OAR) laboratories. They are all online coupled with the Unified Forecast System (UFS, https://ufscommunity.org/), a community-based coupled, comprehensive Earth modeling system. (1) GEFS-Aerosols: the first generation of a coupled aerosol model component was developed in a collaboration between NOAA’s Global Systems Laboratory, Chemical Sciences Laboratory, Air Resources Laboratory, Environmental Modeling Center, and Center for Satellite Applications and Research (GSL, CSL, ARL, EMC, and STAR, respectively) and has been operational since September 2020 as one of the ensemble members of the Global Ensemble Forecast System (GEFS v12.0), with recent updates implemented operationally into the GEFSv12.3 in January 2023. The aerosol component is based on the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) with updates to wet scavenging, anthropogenic and fire emissions and FENGSHA dust schemes. (2) UFS-Aerosols: the second-generation aerosol model component has been collaboratively developed for the UFS by NOAA and NASA’s Global Modeling and Assimilation Office (GMAO) since 2021, and is planned to be implemented into GEFS v13.0 in the coming years. UFS-Aerosols embeds NASA’s 2nd-generation Goddard Chemistry Aerosol Radiation and Transport (GOCART) model. UFS-Aerosols includes the direct and semi-direct radiative feedback from online aerosols prediction by the GOCART model. UFS-Aerosols also has the capability to be fully coupled with ocean, sea ice, and wave components for sub-seasonal to seasonal (S2S) forecasts. (3) UFS-Chem: an innovative community model with the potential for improving chemistry and aerosol processes and thereby predictions of air quality and atmospheric composition. Its initial development, which is a wide collaboration between NOAA OAR laboratories and NCAR, utilizes the Common Community Physics Package (CCPP) infrastructure to link the gas and aerosol chemistry modules to the rest of the model. The enhanced research capabilities of UFS-Chem will include the options to use gas and aerosol chemical mechanisms of varying complexity, ability to easily couple different mechanisms to different physics options, development of a more flexible emissions processing system, and further investment in model evaluation tools that efficiently compare model results against a variety of observations. The capabilities of GEFS-Aerosols, UFS-Aerosols and UFS-Chem for forecasting aerosol optical depth (AOD) and the impacts of aerosols on air quality are evaluated and compared. Observations from reanalysis data, ground-based and aircraft in-situ measurements, and satellite data will be used for these aerosol and gas trace evaluations. The impact of aerosol direct and semi-direct effects on S2S forecast will be evaluated in UFS-Aerosols and UFS-Chem.