New developments to the NASA GEOS Composition Forecasting system

The NASA GEOS Composition Forecast system (GEOS-CF) provides near-real-time analysis and forecasts of global atmospheric composition at 25 km resolution by integrating the GEOS-Chem chemistry model within the NASA Global Modeling and Assimilation Office’s (GMAO’s) GEOS Earth System Model. The system is primarily used for atmospheric chemistry research and to support NASA’s suborbital and satellite missions. For example, GEOS-CF supplies a priori information for the Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite instrument. The GEOS-CF data is publicly available on cloud-based platforms for research, with additional derived products included for applications by, for instance, state and local governments. We present recent advances to the system, which include major updates to the model physics and chemistry and the capability to assimilate satellite observations of ozone, NO₂, and SO₂ from the Microwave Limb Sounder (MLS) and the Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite. We evaluate the system’s performance for key tropospheric and stratospheric species using independent observations from satellites, aircraft, ozonesondes, and surface sites. These updates improve many aspects compared to the earlier system, including reduced biases in the upper tropospheric and lower stratospheric ozone and surface PM_2.5. However, surface ozone shows a persistent high bias, and we investigate the causes.