Mixed-Phase Clouds and Solar Geoengineering

Solar radiation modification techniques aim to counteract the effects of increased greenhouse gas concentrations in Earth’s atmosphere. These techniques typically seek to thin clouds and reduce their heat-trapping effect by increasing the number of so-called ‘ice nucleating particles’ within them. However, adding these particles may have side-effects on other cloud types in the atmosphere. Of particular importance are ‘mixed-phase clouds’ which contain both ice particles and liquid droplets, and are important sources of precipitation, especially over land.

To investigate these processes, this project will use existing instrumentation located at the University of Chicago designed to measure the isotopic composition of water collected at the Pi Cloud Chamber at Michigan Technological University. Water molecules exist in several different varieties, which are nearly indistinguishable in daily life. However, slight differences between the water molecule types can be used to gain insight into cloud processes. Mixed-phase clouds in particular show pronounced changes in isotopic composition as they develop. Cloud chamber-based studies of these clouds will provide a better understanding of how solar radiation modification techniques might affect them and will generate the basic science needed to improve their simulations in cloud models.