Past and future tropical rainfall changes through the lens of storm-resolving climate modeling

Supervisor: Aiko Voigt (Department of Meteorology and Geophysics) in collaboration with Michela Biasutti (Columbia University in the City of New York)

Funding Situation: supervisor has secured funding

Project outline: This study will test the hypothesis that persisting uncertainties in past and future tropical rainfall changes are remedied in storm-resolving climate models. Tropical rainfall is critical to many societies and ecosystems, making it key to climate adaption efforts in a warming world. However, current global climate models are unable to capture past tropical rainfall changes and differ strongly in their projections of future changes. The new class of storm-resolving models operates on grids of ~2km and, in contrast to current models, explicitely simulates convection and many of the associated cloud processes. Motivated by experience from the use of such models in the weather context, this study will address the idea that storm-resolving models provide a step change in our ability to understand past and anticipate future tropical rainfall changes. To this end, the global climate model ICON will be employed in both the new storm-resolving setup and the traditional low-resolution setup to study African rainfall under global warming and during two prominent past episodes: the greening of the Sahara during the mid-Holocene and the Sahel drought of the 1980s. A particular focus will be on mesoscale convective systems, the vertical structure of the tropical overturning circulation and the role of cloud-radiative interactions. The study will build on the international model intercomparison project TRAC-MIP led by Aiko Voigt in collaboration with Michela Biasutti from Columbia University, and further offers the opportunity to interact with colleagues from paleoclimate and geography as well as high-performance computing and data science.