Tornado activity in the US might be connected to the effect of climate change on the Arctic, reports a new research done by the scientists from the University of Illinois at Urbana-Champaign and Purdue University. The study was published recently in the journal Climate and Atmospheric Science.
America has recently experienced a lot of changes in severe-weather behaviour. There has been a significant reduction in the number of tornado touchdowns in the past decade. The study suggests that all the atmospheric circulation changes correspond to loss of ice in the Arctic Sea.
“A relationship between Arctic sea ice and tornadoes in the U.S. may seem unlikely,” said (Robert) Jeff Trapp , who is a professor of atmospheric sciences at the University of Illinois and a co-author of the study. “But it is hard to ignore the mounting evidence in support of the connection.”
For the study, researchers analysed the statistical weather and climate data of the past three decades and saw that there was a strong link between tornado activity and the loss of ice in the Arctic sea- which was especially strong during the month of July.
The research team thinks that this reduction in tornado activity in the US is influenced by how the ice melts in the Arctic control the path of jet stream. The jet stream changes its path to far north while the traditional summer route cover states like Montana and South Dakota. Due to this, atmospheric conditions that lead to tornado formation also change.
“Tornadoes and their parent thunderstorms are fueled by wind shear and moisture,” explained Trapp. “When the jet stream migrates north, it takes the wind shear along for the ride, but not always the moisture. So, even though thunderstorms may still develop, they tend not to generate tornadoes because one of the essential ingredients for tornado formation is now missing.”
“One of the reasons that we focused on sea ice is because, like the ocean and land, it is relatively slow to evolve. Because sea ice and the atmosphere are coupled, the response of the atmosphere is also relatively slow”, added Trapp. “We can use this property to help make long-term predictions for tornadoes and hail, similar to the way predictions are made for hurricane seasons.” But before making these predictions, it is important that scientists understand the cause of changes in sea ice and the role of tropics.
It is still not clear as to why this association can be especially dominant during the month of July. The research team notes that they have only begun understanding how global climate change and climate variability affects severe weather, and will be performing further research.