Science Scoops: Stratospheric Memory!
by Stephen James O'Meara
We've all done it…tried to forecast the weather by looking at the clouds. Indeed, even meteorologists primarily analyze conditions in the troposphere—the lowest layer of the atmosphere, where clouds and storms appear—to predict the weather. Soon, however, they may be setting their sights a little higher.
Mark P. Baldwin, senior research scientist at Northwest Research Associates in Bellevue, WA, says that the key to long-term (weeks to months) weather prediction may be found in the stratosphere—the atmospheric layer just above where commercial airplanes fly. Scientists used to think that the stratosphere is mostly free and clear of weather. Baldwin and his team, however, discovered that significant changes in the troposphere can cause subtle changes in the stratosphere—namely, that they can strengthen or weaken stratospheric wind circulation. And that change will, in turn, affect our weather about 25 days later.
Once the winds in the lower stratosphere become unusually strong or weak, they tend to stay that way for at least a month. And that, Baldwin says, is the key to understanding how the stratosphere can affect our weather. Changes in the stratosphere eventually feed back to the troposphere weeks later through a mechanism dubbed “stratospheric memory.”
The scientists now hope to explore further the interaction between the two layers, which they don't yet fully understand. Knowing that the stratosphere plays this role could be helpful in predicting weather patterns well beyond the 7- to 10-day limit of current weather prediction models. In addition to forecasting the weather, the authors hope that these insights will lead to improved models for tracking global warming, ozone depletion, and the effects of volcanic eruptions.
- How does weather in the stratosphere affect weather in the troposphere?
[anno: Strong winds in the troposphere create small changes in the weather of the stratosphere. Approximately 25 days later, the changes in the stratosphere affect the weather of the troposphere.]
- Why do you think that it is difficult to predict the weather beyond the next seven to ten days?
[anno: Answers may vary but could include that the weather patterns currently change every seven to ten days in the troposphere and that meteorologists, without knowing what is causing changes in the troposphere, can only predict the weather for a short period of time into the future.]
- What else might affect weather in the stratosphere?
[anno: Answers will vary but could include influences from outer space, such as explosions on the surface of the Sun or the amount of space dust hitting the atmosphere.]