Yes, forecasters are often wrong. But there are such weather anomalies that cannot be predicted in advance, for example, due to a lack of knowledge about certain phenomena in the Earth's atmosphere. The European heat wave in 2003, the California drought in 2014, the superstorm Sandy in 2012 - all these catastrophic events, which claimed many lives, were triggered by the phenomenon of blocking jet currents. But until now, scientists have not been able to find a convincing way to explain what is happening.
Jet streams were first discovered by the University of Chicago meteorologist Carl Rossby in the first half of the twentieth century. This term refers to narrow streams of strong wind (on average 45-50 meters per second) in the upper troposphere and lower stratosphere, which have a rather complex structure in the horizontal and vertical directions. Almost simultaneously with the discovery of jet streams, it became known that they can very sharply "slow down".
And so, finally, geophysicist Noboru Nakamura and his graduate student Clare Huang tied the events together. Interestingly, the solution to the problem was a mathematical model describing a kind of traffic jam on a high-speed multi-lane highway.
One of the problems in describing the process of "braking" was the selection of parameters that would most accurately characterize the movement of air masses. The authors of the new work had to add several previously unused parameters, in particular, the meander, that is, the degree of tortuosity of the jet stream. (A similar characteristic is commonly used when describing the river bed.)
Returning to the analogy with road traffic, the researchers discovered the carrying capacity of air masses in the jet stream. Obviously, when the threshold is exceeded, the flow rate decreases. A similar effect occurs when several air "lines" merge.
In a press release from the university, the scientists note that their surprisingly simple model not only explains the blockage of jet streams, but also provides a long-awaited opportunity to predict it. Moreover, we are talking about both short-term weather forecasting and models of long-term behavior of air masses in regions that are prone to frequent droughts or floods.
It is important that the new model, in contrast to most modern climate calculations, turned out to be simple in terms of calculations. At the same time, the authors note that when using it, one should be as careful as possible to the meteorological features of a particular region. In particular, in the Pacific Ocean "air jams" can dissolve for decades.
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You can learn more about the achievements of the Chicago geophysicists by reading their article published in Science.
Daria Zagorskaya