The walls would need to be about 1,000 feet high and 150 feet wide.
Forget the Great Wall of China. How about the Great Wall of ... Kansas?
One scientist thinks we can protect parts of the central USA from ferocious tornadoes by building several gigantic walls across Tornado Alley:
"If we build three east-west great walls in the American Midwest .... one in North Dakota, one along the border between Kansas and Oklahoma to the east, and the third one in south Texas and Louisiana, we will diminish the tornado threats in the Tornado Alley forever," according to physicist Rongjia Tao of Temple University.
The walls would need to be about 1,000 feet high and 150 feet wide, he said. Tao is presenting his research next week at the annual meeting of the American Physical Society in Denver.
He said that major tornadoes in Tornado Alley are created from the violent clashes between the northbound warm air flow and southbound cold air flow. He adds that because there are no west-to-east mountains in Tornado Alley to weaken the air flow, collisions between warm and cold air create turbulence and supercells that spawn tornadoes.
Tornado Alley is generally defined as the Plains states from the Dakotas to Texas.
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The walls would stop the flow of air from north and south, thus preventing the tornadoes from forming, he said. As an example he cites China, where east-west mountain ranges help reduce tornadoes there.
Naysayers abound. Aside from the cost of $60 billion per 100 miles (according to Tao's estimates) and huge engineering challenges, "it wouldn't work," tornado researcher Harold Brooks of the National Severe Storms Laboratory in Norman, Okla., said in an e-mail.
Brooks said that China has deadly tornadoes despite the east-west mountain ranges there. In addition, he said, tornadoes still occur in parts of Oklahoma, Arkansas and Missouri despite the presence there of smaller east-west mountain ranges similar in size to Tao's proposed walls.
"If his hypothesis was true, we'd already have the thing he wants to build naturally," Brooks said.
"This is essentially a case of a physicist, who may be very good in his sub-discipline, talking about a subject about which he is abysmally ignorant," Brooks said.
Another expert, meteorologist Mike Smith of AccuWeather Enterprise Solutions, also called the theory "nonsense."
"The old cold air hitting warm air canard," Smith wrote on his blog. "That is misleading at best, especially since most of the violent Plains thunderstorms occur along a 'dry line' where there is a relatively small temperature difference."
He also said that "if supercell thunderstorms with F-5 tornadoes could laugh, they would have a hearty chuckle as they 'attacked' the wall. If tornadoes can go up and down mountains (and they can!), they would go over/through the wall."