Lightning HOx: Laboratory and Photochemical Modeling Studies of Hydroxyl (OH) and Hydroperoxyl (HO2) Generated by Atmospheric Electrical Activity

This project focuses on laboratory experiments to study the generation of extremely reactive chemical species, known as radicals, that are formed during lightning. An atmospheric radical is a very reactive atom or group of atoms that has the ability to remove or change many pollutants in the atmosphere. The goal of this research is to understand the conditions under which these radicals are produced by lightning and how they influence global and regional atmospheric chemistry. Atmospheric radicals are important because they affect the lifetimes of pollutants and greenhouse gases in the atmosphere.

Laboratory generated electrical sparks and corona over a wide range of conditions will be used to study lightning-generated NOx (LNOx) and lightning-generated HOx (LHOx). The ratio LHOx/LNOx will be measured as will its dependence on: (a) spark intensity, frequency, length, radius, and number; (b) corona intensity and spatial extent; (c) time between generation point and the chemical sensors; (d) the ratio of HOx/NOx production as a function of all of these factors; (e) the relationships among the production of HOx, NOx, and O3; (f) the relationships of the production of HOx, NOx, and O3 to spark and corona characteristics; (g) the influence of pressure, water vapor, and OH reactivity on these relationships and on the calculated OH exposure; and (h) the OH exposure measured by decreases in a volatile organic compound (VOC).

These laboratory measurements will be simulated with photochemical box models to determine the initial HOx/NOx ratio and the resulting OH exposure for comparison with measured values. The information from these laboratory and modeling studies will be parametrized for inclusion in a global chemical transport model, which will be used to understand the global and regional implications of LHOx on atmospheric oxidation.

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.