From the NASA/GODDARD SPACE FLIGHT CENTER and the “how long until global warming is blamed” department.
A 60-year pattern in the stratosphere changes up
“The quasi-biennial oscillation is the stratosphere’s Old Faithful,” said Paul Newman, Chief Scientist for Earth Sciences at NASA’s Goddard Space Flight Center, Greenbelt, Maryland, and lead author on a new paper about the event published online in Geophysical Research Letters. “If Old Faithful stopped for a day, you’d begin to wonder about what was happening under the ground.”
Winds in the tropical stratosphere, an atmospheric layer that extends from about 10 to 30 miles above Earth’s surface, circulate the planet in alternating easterly and westerly directions over roughly a two-year period. Westerly winds develop at the top of the stratosphere, and gradually descend to the bottom, about 10 miles above the surface while at the same time being replaced by a layer of easterly winds above them. In turn, the easterlies descend and are replaced by westerlies.
This pattern repeats every 28 months. In the 1960s scientists coined it the “quasi-biennial oscillation.” The record of these measurements, made by weather balloons released in the tropics at various points around the globe, dates to 1953.
The pattern never changed – until late 2015. As the year came to a close, winds from the west neared the end of their typical descent. The regular pattern held that weaker easterly winds would soon replace them. But then the westerlies appeared to move upwards and block the downward movement of the easterlies. This new pattern held for nearly half a year, and by July 2016 the old regime seemed to resume.
“It’s really interesting when nature throws us a curveball,” Newman said.
The quasi-biennial oscillation has a wide influence on stratospheric conditions. The amount of ozone at the equator changes by 10 percent between the peaks of the easterly and westerly phases, while the oscillation also has an impact on levels of polar ozone depletion.
With this disruption now documented, Newman and colleagues are currently focused on studying both its causes and potential implications. They have two hypotheses for what could have triggered it – the particularly strong El Niño in 2015-16 or the long-term trend of rising global temperatures. Newman said the scientists are conducting further research now to figure out if the event was a “black swan,” a once-in-a-generation event, or a “canary in the coal mine,” a shift with unforeseen circumstances, caused by climate change.
The EOS article on the strange pattern:
The paper is available at:
The prevailing winds in the atmosphere near the equator above about 17 km are known to undergo a slightly irregular oscillation from strong westerlies to strong easterlies roughly every other year. This Quasi-biennial Oscillation (QBO) has been observed to dominate the winds in this region of the atmosphere for at least the last 6 decades and is characterized by a downward propagation of the westerly and easterly jets that form. This video allows a 3D vizualization of the behavior of the QBO jets. Specifically what is shown are regions of strong westerlies/easterlies outlined by the red/blue surfaces. The long term mean seasonal cycle are subtracted from the data and surfaces are plotted only equatorward of 30 degrees. The height range plotted is about 17-36 km. Results are shown for 1980-2000.