UFS-RAQMS global atmospheric composition model: TROPOMI CO column assimilation

Abstract. This paper describes a new version of the Real-time Air Quality Modeling System (RAQMS) which uses National Unified Operational Prediction Capability (NUOPC) coupling to combine the RAQMS chemical mechanism with the Global Ensemble Forecasting System with Aerosols (GEFS-Aerosols), the Goddard Chemistry Aerosol Radiation and Transport model (GOCART) aerosol mechanism, and NOAA's Unified Forecast System (UFS) version 9.1 Finite Volume Cubed Sphere (FV3) dynamical core. We also present an application of TROPOMI CO column data assimilation in UFS-RAQMS with the NOAA Grid Point Statistical Interpolation (GSI) three-dimensional variational (3D-Var) analysis system to constrain UFS-RAQMS CO. We validate UFS-RAQMS control and TROPOMI CO data assimilation CO analyses for the period 15 July–30 September 2019 against independent satellite, ground-based, and airborne observations. We show that the largest impacts of the TROPOMI CO data assimilation are in the lower troposphere over Siberia and Indonesia. We find that UFS-RAQMS biomass burning signatures in CO column are not consistent with those in aerosol optical depth (AOD) near the Siberian and Indonesian biomass burning source regions within our control experiment. Assimilation of TROPOMI CO improves the representation of the biomass burning AOD/CO relationship in UFS-RAQMS by increasing the CO column, which suggests that the biomass burning CO emissions from the Blended Global Biomass Burning Emissions Product (GBBEPx) used in UFS-RAQMS are too low for boreal wildfires.