The quasi-biennial oscillation, a stratospheric wind pattern, changed this year for the first time since scientists began monitoring it. Photo: Shutterstock
The stratosphere is the layer of the atmosphere between about 10 and 30 miles above the surface of the Earth. Over the tropics, there is an event called the quasi-biennial oscillation, which scientists have been observing since the 1950s. This event is actually pretty simple, every 28 months or so, westerly winds at the top of the stratosphere move downward and are replaced by easterly winds, which then do the same. It’s happened with absolute regularity since the day scientists began observing it.
But there was a slight hiccup this year. In late 2015, the westerly winds should have been replaced by easterly winds, but instead they moved back, blocking the weaker easterly winds and holding that new pattern for about half a year.
Things went back to normal in July, but this change has left scientists wondering why it happened. They’ve been observing the same pattern for more than 60 years, so when that pattern is interrupted, they start to wonder why. Was it a one-time event, perhaps caused by the recent powerful El Niño? Or is it a more permanent change brought on by global climate change?
At this time the scientists don’t have answers, but they’re certainly interested in finding some. If it’s a one-time fluke, it could be interesting, but it isn’t going to affect anyone’s life very much. In fact, the change had no real impact on weather patterns as we experience them here on the earth’s surface.
That isn’t to say, however, that it might not have an impact in the long run, especially if the cycle undergoes a substantial, lasting shift. Even if the pattern goes back to normal right away, it could indicate that something new is happening in the stratosphere, which could be caused by the changing global climate. The only way to know is to investigate the issue at length, which NASA is already interested in doing.
This change to the quasi-biennial oscillation leaves scientists thinking that it’s time to learn more about stratospheric weather and how it affects—or is affected by—the climate on the earth’s surface.