NOx And Lightning

Left: The worldwide distribution of lightning strikes. Each flash produces a tiny puff of NOx, individually negligible, but adding up to as much as 20 trillion grams per year when summed over the entire globe.



An old grad school classmate, William Koshak, pops up in NASA's Science News!:

"Atmospheric chemists are very interested in trace gases produced by lightning, particularly nitrogen oxides ('NOx' for short)," explains William Koshak, a lightning researcher at NASA's Marshall Space Flight Center. NOx includes nitric oxide (NO), a toxic air pollutant produced by automobile engines and power plants, and nitrogen dioxide (NO2), a poisonous reddish-brown gas with a sharp odor.

"We know that lightning is the most important source of NOx in the upper troposphere, where our weather takes place," Koshak continues. "NOx indirectly influences our climate because it partly controls the concentration of ozone (O3) and hydroxyl radicals (OH) in the atmosphere. Ozone is an important greenhouse gas, and OH is a highly reactive molecule that controls the oxidation of several greenhouse gases."

While the output from cars and industry can be measured, lightning is a wildcard in models of regional air quality and global climate because it is difficult to realistically model several important lightning characteristics--e.g., lightning energy and the thermochemical yield of NOx produced by a lightning stroke. As such, the global production rate of lightning NOx is still uncertain, and ranges anywhere from 2 to 20 teragrams per year (1 teragram = 1 trillion grams).