ICON-HAM-lite 1.0: simulating the Earth system with interactive aerosols at kilometer scales

Abstract

Aerosols strongly influence Earth’s climate as they scatter and absorb radiation and serve as nuclei for cloud droplets and ice crystals. New Earth system models that run at kilometer resolutions allow us to examine long-standing questions related to these interactions. To perform kilometer-scale simulations with the Earth system model ICON-MPIM, we developed the one-moment aerosol module HAM-lite. HAM-lite was derived from the two-moment module HAM. Like in HAM, aerosols are represented as an ensemble of lognormal modes. Unlike in HAM, aerosol sizes and compositions are prescribed, which reduces the computational costs significantly. Here, we present a first global simulation with four aerosol modes at a resolution of 5 km over a period of 1 year. The simulation captured key aerosol processes including, for example, the emission of dust aerosols by cold pool outflows in the Sahara and the interaction of sea salt aerosols and shallow convective storms around the doldrums.