Solar Climate Intervention: Establishing baseline metrics for the lower stratosphere using the heliotrope solar hot air balloon system

Abstract:

The climate impacts associated with solar climate intervention strategies are primarily based on global models which have known biases. Through this work, we aim to develop a new capability to sample stratospheric air for increased knowledge and understanding of the lower stratosphere in order to improve our understanding of model bias and behavior in this region. In addition, we aim to develop rapidly deployable, standardized instrumentation payloads that can be used to sample the lower stratosphere to establish baseline metrics. Using Sandia’s 'heliotrope' solar hot air balloon system, we field lightweight atmospheric measurement equipment to sample the stratosphere. The heliotrope is made up of lightweight plastic and the interior coated with charcoal powder. The system is inflated with ambient air which is then heated through incoming solar radiation. Once the envelope becomes positively buoyant, it is lifted to the lower stratosphere, where it floats, directed by the winds, until the sunset terminates the flight. Depending on envelope size, the heliotrope can take up to a few kilograms to 16-23 km altitude. The stratospheric observations on these flights include measures of the pressure, temperature, humidity, aerosol optical particle counts, and gas concentrations. Here we present lessons learned in field campaign preparation and instrumentation development and the results from four field campaigns deployed from New Mexico during the 2020 calendar year. The heliotropes reached altitudes of 19-23 km and sampled the ambient air for 11-13 hours.