Impacts of Stratospheric Aerosol Injection on Convection, Precipitation, and Clouds: A Model Hierarchy Approach

PI: Malte Jansen
Research scientist: Seth Seidel
Collaborator: Da Yang, Assistant Professor, Geophysics, Stanford University

Stratospheric aerosol injection (SAI) is designed to cool the planet by reflecting sunlight. In addition to this cooling effect, the aerosols also heat the lower stratosphere, which may alter atmospheric circulation, cloud formation, and the global water cycle.

This project examines two related questions: how stratospheric warming affects convection and precipitation, and how it changes high-altitude clouds and their role in Earth’s energy balance.
Stratospheric warming can lower the tropopause and reduce the total cooling of the lower atmosphere. This may weaken rainfall and reduce the energy that drives atmospheric motion. At the same time, warming in the upper atmosphere may change the structure and coverage of high-altitude clouds such as cirrus. These clouds influence how much heat is trapped in the atmosphere and how much sunlight reaches the surface.

The research uses a model hierarchy approach to study these effects across different scales:

• Single-column models to identify the fundamental physical mechanisms linking heating, convection, and precipitation
• High-resolution cloud-resolving models to simulate how cloud systems evolve under SAI conditions
• Global climate models to assess large-scale climate responses and regional patterns
• Super-parameterized models to better connect cloud-scale processes with global circulation

By testing each hypothesis across this hierarchy of models, the team can identify where predictions agree or differ, reducing uncertainty and improving confidence in the findings.