Blockages in the global air currents called the jet streams could explain why we experience strange and sometimes deadly weather pattern, according to new study by atmospheric scientists at University of Chicago.

The jet stream has a capacity, and when it’s exceeded it, blockages form that are similar to traffic jams can occur. The 2003 European heat wave, California’s 2014 drought and Superstorm Sandy in 2012  were caused by this same weather phenomenon known as “blocking.” The phenomenon is extremely difficult to predict, and there was no compelling explanation on why and when it forms.

The Northern Hemisphere's polar jet stream. [Image: NASA's Goddard Space Flight Center]

In the study, researchers came up with a set of equations in order to analyze the phenomenon, one of which was to measure the jet stream’s meander.  Upon checking the equation, the team realized that it was almost identical to the one created decades ago by transportation engineers to describe traffic jams.

They found that just as highway has traffic capacity, the jet stream has ‘weather traffic’ capacity, and on exceeding it, blocking manifests as congestion. Traffic slows down when multiple highways merge; the same can happen to the jet stream due to topography such as mountains or coasts.

“The result is a simple theory that not only reproduces blocking, but predicts it,” said the study coauthor Noboru Nakamura, a professor in the Department of the Geophysical Sciences, who called making the cross-disciplinary connection “one of the most unexpected, but enlightening moments in my research career — truly a gift from God.”

Their findings may not efficiently forecast short-term weather patterns for now, but the team says it can certainly help predict long-term patterns, including the areas that may see more drought or floods. Climate change influences this blocking phenomenon by pushing the jets stream closer to its capacity, but there will be regional differences: the Pacific Ocean may experience a decrease in blocking over the decades, the researchers noted.

“It’s very difficult to forecast anything until you understand why it’s happening, so this mechanistic model should be extremely helpful,” Nakamura said.

And the model, unlike most modern climate science, is computationally simple: “This equation captures the essence with a much less complicated system,” said Clare S.Y. Huang, another researcher who was involved in the study.

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