Possible Effects of Ammonium on Lightning Properties

Numerous studies have addressed the presence of the so called “anomalous” polarity storms over the US Great Plains. It is over this region that the Cloud-to-Ground (CG) lightning flash polarity exhibits a unique preponderance for positive CG flashes. Thermodynamical storm proxies have been almost unanimously accepted as the major players in dictating the aforementioned lightning behaviour. Apart from lightning, the GP region possesses another unique property. Maps of Environmental Protection Agency highlight that the US Great Plains is a major recipient of ammonium (NH4+) in rainwater, as a consequence of the extensive agricultural and livestock farming over the area. The author has come across an intriguing observation; A hand full of peer-reviewed laboratory-based studies document that the presence of soluble ions such as ammonium favor the positive charging of graupel, while consequent particle collisions lead the ice crystals to acquire a negative charge. If one extrapolated the latter into the “non-sterile” atmosphere, the presence of NH4+ could arguably lead the enhancement of anomalous polarity storms hence +CG presence. Although the marked spatial coherency between these two parameters over the US GP does not establish causality, it contextualizes a well-educated speculation of a physical process that may act independently from the well-established thunderstorm charging mechanisms.