Increasing Confidence for Stratospheric Aerosol Experiments: Improvements in Flight Turbulence Simulations to Establish Realistic Expectations for the Future Operation of SCoPEx

Abstract

Continued emissions of greenhouse gases and the absence of stringent action from global policymakers has given the world little time to combat the worst climate change has to offer. In order to give ourselves more time, researchers propose methods in solar geoengineering that will increase the reflectivity of the planet and actively cool the Earth. One such method involves emitting a thin layer of aerosol in the stratosphere, where aerosol backscattering effects will be effective in limiting the increase of global average temperatures even if humans double the amount of CO2 currently in the atmosphere. However, potential risks of this method include the depletion of the ozone layer or unwanted heating in the lower stratosphere, and the extent to which this may occur with solar geoengineering is uncertain. Current chemical transport models are trying to better understand this risk but require better data on aerosol behavior in the stratosphere to improve their simulations. The Stratospheric Controlled Perturbation Experiment (SCoPEx), led by researchers at Harvard, aims to help gather this crucial data but cannot begin flight tests until the risks of this experiment are better understood. A core risk was a poor understanding of flight turbulence in the stratosphere, so for this project, we constructed realistic expectations of this phenomenon by simulating the real propeller geometry of the SCoPEx device and by implementing the effects of background gravity waves. The simulations ran provided a more clearer picture of how much turbulence is actually generated by the propellers, and we found that gravity waves did not have a meaningful impact on turbulence in these simulations. Soon, these simulations will be greatly improved by adding even more geometrical complexity and by combining these solutions with chemical transport models. Hopefully these efforts will provide enough technical data to greenlight future SCoPEX operations so that crucial experimental data can be collected for the solar geoengineering research community.