Phys.org June 27, 2024
Central North America is the global hotspot for tornadoes, fueled by elevated terrain of the Rockies to the west and a source of warm, moist air from equatorward oceans. Based on this theory central South America, with the Andes to the west and Amazon basin to the north, should have a “tornado alley” at least as active as central North America. Central South America has frequent severe thunderstorms yet relatively few tornadoes. According to a team of researchers in the US (Purdue University, National Center for Atmospheric Researchers, (Boulder, CO), Stony Brook University, Colorado State University) this theory is missing an important ingredient specific to tornadoes: a smooth, flat ocean-like upstream surface. They showed that central South American tornado potential substantially increases if its equatorward land surface was smoothed and flattened to be ocean-like. Central North American tornado potential substantially decreases if its equatorward ocean surface was roughened to values comparable to forested land. According to the researchers their findings indicate that large-scale upstream surface roughness is likely a first-order driver of the strong contrast in tornado potential between North and South America… read more. TECHNICAL ARTICLE
Credit: Unsplash/CC0 Public Domain.