Toward a Simulation of Variable Dust Mineral Composition in the NASA Goddard Earth Observing System Global Model

The Goddard Earth Observing System (GEOS) is a global Earth system model suitable for a range of aerosol-chemistry applications. Within GEOS, the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) module has been run online for a number of years. GOCART treats the sources, sinks, distributions, and Earth system (e.g., radiative, moist physics) impacts of dust, sulfate, sea salt, nitrate, and carbonaceous aerosol species. The GOCART module has been extended over time to allow for tracer “tagging,” making it possible to track aerosol and chemical species from specific source regions or source types for apportionment and impact studies. Here we report how this tagging capability is being extended in the dust scheme to track mineral dust composition. The baseline version of the dust scheme within GOCART carries five different non-interacting tracers to track the evolution of the dust particle size distribution, but a limitation of that scheme is that all the dust is assumed to be of the same composition regardless of its source region. Recently available datasets are being used here to link soil mineral composition to the aerosol mode, and we show preliminary work in the GEOS system toward developing that capability. Our main interests are to find a minimal set of composition elements needed to track the mineral components important for dust-radiation interactions, and then to use that capability to impact the dust radiative forcing simulated in the model. An additional example of the multi-component dust impact on simulated top-of-atmosphere radiances for the space-based Ozone Monitoring Instrument (OMI) is presented.