Impacts of Stratospheric Aerosol Injection on Precipitation: A Model Hierarchy Approach

PI: Tiffany Shaw
Collaborator: Da Yang, Assistant Professor, Geophysics, Stanford University

Stratospheric aerosol injection (SAI) has been proposed as a way to cool the Earth by reflecting a small portion of incoming sunlight. At the same time, these aerosols warm the lower stratosphere, which can shift the structure of the atmosphere and influence rainfall around the world.

This project focuses on a central question: how would SAI change global precipitation?

Stratospheric warming may lower the tropopause and reduce the amount of heat the lower atmosphere releases to space. Because this heat loss helps drive rainfall, a reduction could weaken the global hydrological cycle and lead to less precipitation overall.

To understand this process, the research uses a model hierarchy approach that examines the problem across multiple levels of complexity:

• Single-column radiative-convective models to isolate the fundamental physical links between atmospheric heating, cooling, and precipitation
• Cloud-resolving models to test how these processes behave in more realistic atmospheric conditions
• Global climate models to examine how precipitation changes vary across different regions

Across these models, the team will test different SAI scenarios, including sunlight reflection alone, stratospheric heating alone, and the combination of both. By connecting basic physical principles to global climate patterns, this project aims to provide clearer and more reliable estimates of how SAI could reshape rainfall worldwide.