An Improved Representation of Organic Aerosol Composition in the ECMWF IFS-COMPO

Organic compounds constitute roughly half of the submicron aerosol mass in the troposphere, highlighting the need for accurate representation of organic aerosol (OA) in atmospheric composition (AC) modeling systems to improve aerosol forecasting. The secondary fraction of OA (SOA), formed through the oxidation of various volatile organic compounds (VOCs) from both natural and anthropogenic sources, complicates OA simulation. However, most global AC models either assume a nonvolatile SOA produced with a constant yield from known precursors or provide a simplistic parameterization of its volatility, treating the primary fraction of OA (POA) as nonreactive. This approach often fails to accurately reproduce observed OA atmospheric measurements. Additionally, primary biological aerosol particles are commonly identified as part of the supermicron OA mass, although most global AC models inadequately represent them.

In the context of the Copernicus Atmosphere Monitoring Service, we focus on improving the OA representation in the CAMS global forecasting system (IFS-COMPO). We here present simulations of the partitioning and chemical evolution of POA vapors, including their changes in volatility, as well as the incorporation of coarse organic carbon emissions from major bioaerosol species. The formation of SOA from semi-volatile organic compounds (SVOCs) and intermediate-volatility organic compounds (IVOCs) has been integrated into the SOA formation schemes from biogenic and anthropogenic VOCs in IFS-COMPO using a lite version of the well-documented aerosol module ORACLE, which allows for relatively limited computing resources. Additionally, fungal spores and pollen grains have been included in IFS-COMPO through interactive emission schemes that depend on ecosystem types, the leaf area index (LAI), and meteorological parameters. Overall, our efforts aim to bridge the gap between model simulations and observations, thereby enhancing our understanding of the atmospheric organic carbon burden.