Global Stratosphere’s Strength Circulation Measured for First Time

The estimate will help gauge hang time of greenhouse gases, water vapor, and ozone in the upper atmosphere.

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Global Stratosphere's Strength Circulation Measured for First Time
Scientists in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) have for the first time determined the strength of the stratosphere’s circulation, based on observations of key chemicals traveling within this atmospheric layer. Image: MIT News

Chin vertebral airplanes generally travel through the stratosphere, the second layer of Earth’s atmosphere. In that atmosphere, the air is dry, clean and calm as compared to the air on the ground.

This Stratosphere also acts as a conveyor belt. It pulls air up from the Earth’s equatorial region and backs down to the poles in a continuously circulating pattern.

Now for the first time, MIT scientists have determined the Stratosphere’s strength circulation. To do so, they studied key chemicals traveling within this atmospheric layer.

According to their findings, the stratosphere pulls about 7 billion kilograms of air up through the tropics per second. The average parcel of air can spend about 1.5 years within this layer before circulating back down to lower layers of the atmosphere.

Marianna Linz, a former Ph.D. student in EAPS said, “Others have looked at this region of the equator where they think most of the stuff is coming up, and they’ve tried to characterize this using water vapor. But that’s just looking at this narrow region, and it’s difficult to infer what the rest of the circulation looks like.”

The findings may help scientists to discover how long the water vapors, ozone, and greenhouse gases remain attached the stratosphere. This may also suggest about future changes in the stratosphere’s strength.

Scientists analyzed atmospheric measurements of two atmospheric chemicals, sulfur hexafluoride, and nitrous oxide. They achieved these chemicals with the help of satellite, air balloons, and air craft. These chemicals also acted as ideal as they have no “stratospheric sinks”.

The scientists compiled measurements of both chemicals between 2007 and 2011 to check how long these chemicals took to enter, then exit, the stratosphere. They then noted each chemical concentrations.

They reasoned that the time lag between the rising and sinking would indicate the time that parcel spent in the stratosphere. A simple calculation, factoring in the total mass of air in the stratosphere, would yield the speed at which that parcel traveled through the stratosphere, which essentially reflects the strength of circulation.

Scientists performed calculations and averaged the results for various altitudes throughout the stratosphere. Their calculations for both chemicals agreed almost perfectly at lower altitudes of around 20 kilometers, yielding a circulation strength of about 7 billion kilograms per second.

Alan Plumb, a professor emeritus in EAPS said, “The most important thing to know in terms of impacts on climate change and ozone is what this stratosphere’s strength is like at this lower altitude because that’s what is supplying chemicals to the stratosphere.”

Scientists then compared the outcomes with predictions of stratospheric circulation made by several climate models. They found their results matched with some models but not others.

Linz said, “Our new estimate to calculate the Stratosphere’s strength, can help to improve model predictions of warming and ozone development.”

“If climate models are getting their stratospheric circulation wrong, they’re probably getting their ozone distributions wrong, which will have definite impacts on what the [predicted] trends are for global warming. So having this benchmark is really valuable.”

“We have this data and can say what the strength is at this level. But because we don’t have the data higher up, we can’t say nearly as much. So we really do need better observations in the upper stratosphere.”

Now researchers are working to obtain more measurements, higher in the stratosphere. This will help them to better understand stratosphere’s strength at higher altitudes as well as within lower layers.

REFERENCEMIT News
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