The United States may experience more tornadoes than any other country in the world due to its geographical location and terrain.
Recent research published in the journal Earth, Atmospheric and Planetary Sciences discovered that a smooth, flat surface akin to an ocean could explain why the U.S. has the highest number of tornadoes globally, reported Newsweek on June 20.
The U.S. experiences over 1,200 tornadoes per year, three to four times more than all other countries combined. (Image: Business Insider).
Tornadoes can form during any type of severe thunderstorm, although they most frequently result from supercell storms (a rare storm phenomenon characterized by continuously rotating clouds accompanied by hail, strong winds, and lightning). Supercell storms are intense, vertically-oriented rotating systems that can last for extended periods. In these storms, tornadoes can form either from bottom to top or from top to bottom.
North America is a global hotspot for tornadoes. This is due to the combination of the Rocky Mountains in the west and the influx of warm, moist air from the Gulf of Mexico, creating an ideal geographical setup for extreme thunderstorms that generate tornadoes. South America also has similar conditions with the Andes Mountains in the west and warm, moist air from the Amazon Basin moving northward. However, despite frequent severe thunderstorms, South America experiences significantly fewer tornadoes.
Researcher Funing Li from the Massachusetts Institute of Technology and colleagues investigated how terrain roughness in areas above tornado hotspots affects tornado risk. They used global climate models to simulate various surface conditions, such as regions near the equator in South America’s tornado hotspot. The research team modeled smooth, ocean-like surfaces and found an increased likelihood of tornado formation. Conversely, in the area known as the Storm Corridor in North America, they simulated rough, forest-like surfaces and found a reduced tornado risk.
The new study indicates that the smooth and flat terrain in upstream regions is a key factor in tornado formation. This may explain why the U.S. records one of the highest numbers of tornadoes in the world. Understanding why tornado hotspots arise is essential for predicting how they may change due to climate change. Previous studies have found that global warming exacerbates the ideal conditions for extreme thunderstorms. However, tornadoes are challenging to predict, meaning there is still much uncertainty regarding the factors influencing them.
