Anthropogenic aerosol effects on extreme precipitation in the tropics in ICON HAM-lite global km-scale simulations

Natural and anthropogenic aerosols influence Earth’s climate through many different radiative and cloud microphysical processes; directly by scattering and absorbing radiation and indirectly by serving as cloud condensation and ice nuclei. They are thought to influence precipitation on global to local scale, but the mechanisms governing their effects and their relative importance remain highly uncertain, lowering the confidence in future projections on smaller scales. Understanding how aerosols affect extreme precipitation is especially important, given its potential large societal impacts, but while many Earth system models include complex aerosol-radiation-cloud processes and feedbacks, smaller scale processes are not explicitly resolved and instead parameterized. However, the newer generation of km-scale cloud-resolving Earth system models allow for these processes to be studied in much greater detail.

In this study we analyze results from 1-year global km-scale simulations run using ICON coupled to HAM-lite, a one-moment aerosol module derived from the two-moment module HAM. The simulations are run with prescribed pre-industrial and present-day aerosol emissions, allowing us to investigate the impacts of anthropogenic aerosols on extreme precipitation. Preliminary results indicate a strengthening of extreme precipitation rates in the tropics in the present-day simulation compared to the pre-industrial control, with regional differences that will be explored further to distinguish between large-scale dynamical changes and local convective changes.