The primary author of the paper is Walter Lyons of the Yucca Ridge Field Station in Fort Collins, Colorado. Ordinarily, thunderstorms produce negative flashes to the ground. Between April and June, nearly half a million flashes in the southern plains were positively charged. These thunderstorms also produced abnormally high numbers of mesospheric optical sprites, the fleeting red glows that appear between 30 and 90 km above the ground in association with thunderstorms. One mesoscale convective system over Nebraska, on 20 May 1998, produced 380 sprites, the highest single-storm total recorded in more than 100 storms and six years of observations.
Smoke provides cloud condensation nuclei, particles of matter on which cloud vapor condenses.
When a large amount of smoke, soot, contaminants, or aerosols is in the atmosphere, the elevated numbers of CCNs can affect droplet size, which in turn can affect various aspects of the charge separation mechanisms, according to the paper's authors. The research team also includes Thomas Nelson of the Yucca Ridge Field Station and John Cramer and Tommy Turner of Global Atmospherics in Tuscon, Arizona. The research was conducted in part with support from NSF, NASA, and the U.S. Department of Energy. While this work may appear to offer hope for the ability of trees to absorb increasing amounts of carbon dioxide from fossil-fuel combustion and deforestation, researchers caution that the growth rate likely cannot be sustained. In fact, it already appears to be stabilizing.