Field Measurements for Understanding Atmospheric Oxidation Generated by Electrical Discharges

The goal of this project is to use UV radiation flux measurements to determine the production of hydrogen oxide radicals (HOx) from sources such as corona on trees under thunderstorms and on high voltage electrical power transmission lines. Because direct HOx measurements are difficult to obtain, the use of coronal UV radiation as a surrogate for HOx production can help build an understanding of the contribution of electrically generated HOx to atmospheric oxidation. Hydrogen oxide radicals (especially the hydroxyl radical OH) are important oxidizing species that control the concentrations of toxic gases like carbon monoxide and climate relevant gases like methane. Previously, the project team conducted laboratory studies to measure HOx emissions from electrical and corona discharges on metal objects and on different types of tree leaves. In this project, they will explore field measurements of UV emissions from and in thunderstorms and associated electrified anvils. They plan to use the following two approaches: (1) ground-based measurements using a solar-blind UV camera and a Corona Observing Telescope System recently built by the team; and (2) balloon-borne measurements of UV radiation in the 180-195 nm band and the 240-280 nm band using small solar-blind detectors accompanied by a video camera, and measurements of pressure, temperature, dewpoint temperature, sound, and GPS location. The UV radiation measured from electrical discharges from balloons will quantify the UV radiation field, and thus HOx production, in thunderstorm cells and anvils. The project team aims to: (1) ensure that all significant atmospheric HOx-producing electrical discharges have been identified; and (2) substantially reduce the uncertainties in calculating atmospheric electrical discharge impacts on atmospheric oxidation. The project includes support for an undergraduate and graduate student, and a postdoc, who will be trained to participate in the planned research. This effort has great potential for new interdisciplinary research efforts that bridge between atmospheric chemistry and physical meteorology, forestry, plant biology, and electrical engineering. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.