Blog Archive

Saturday, August 11, 2012

Water vapor belches over the North and South Poles

These animations absolutely stunned me the first time I saw them, and truth be told, they still awe me.

The first is an animation of the water vapor cycle over the globe -- notice the way the Earth seems to breathe as the solar equator moves north and south.

At the poles, WV concentrates above the Arctic during December-January, and above Antarctica during June-July.

It is easier to see what occurs at the poles if you look at this animation frame by frame (each month is one frame).

Water Vapor

Water Vapor
July 2012July 2002
Skip to beginning
Step back one
Step forward one
Skip to end

Let this QuickTime file load up and watch the polar vortex being divided in two (animation on the left) while hot air shoots up 30,000 m and temperatures up there go from -88 C to +12 C! (animation on the right).  I call this an atmospheric water vapor belch.

This past January, I was able to download a satellite photo of the Arctic that appeared to show this sort of mechanism in action:

Notice all the leads in the sea ice -- that stuff used to be so pristine looking before 2007.

These satellite photos come from the Canadian weather service and are updated every few hours:

UPDATE:  A commenter named Peter says that the grey areas at the poles are areas not covered by the satellites in the darkness of winter.  Would anyone else care to comment on this?


Peter said...
You're flat-out wrong. The grey areas showing over the North Pole in (NH) winter and the South pole in (SH) winter are areas with no data coverage. Presumably the satellite used (MODIS) can't get adequate data in the dark.

You can tell it's missing data because it's pure grey rather than a shade of yellow.
Peter, I am not sure why you think the MODIS satellite was used.  Other researchers have used the Aqua satellite that uses infrared.  Some satellites use radar or microwaves.  See, for example, this article:

Water Vapor Confirmed as Major Player in Climate Change
Still from animation showing global distribution of atmospheric water vaporThe distribution of atmospheric water vapor, a significant greenhouse gas, varies across the globe. During the summer and fall of 2005, this visualization shows that most vapor collects at tropical latitudes, particularly over south Asia, where monsoon thunderstorms swept the gas some 2 miles above the land.
Credit: NASA
> Watch video
Water vapor is known to be Earth’s most abundant greenhouse gas, but the extent of its contribution to global warming has been debated. Using recent NASA satellite data, researchers have estimated more precisely than ever the heat-trapping effect of water in the air, validating the role of the gas as a critical component of climate change.

Andrew Dessler and colleagues from Texas A&M University in College Station confirmed that the heat-amplifying effect of water vapor is potent enough to double the climate warming caused by increased levels of carbon dioxide in the atmosphere. 

With new observations, the scientists confirmed experimentally what existing climate models had anticipated theoretically. The research team used novel data from the Atmospheric Infrared Sounder (AIRS) on NASA’s Aqua satellite to measure precisely the humidity throughout the lowest 10 miles of the atmosphere. That information was combined with global observations of shifts in temperature, allowing researchers to build a comprehensive picture of the interplay between water vapor, carbon dioxide, and other atmosphere-warming gases. The NASA-funded research was published recently in the American Geophysical Union's Geophysical Research Letters.

"Everyone agrees that if you add carbon dioxide to the atmosphere, then warming will result,” Dessler said. “So the real question is, how much warming?" 

The answer can be found by estimating the magnitude of water vapor feedback. Increasing water vapor leads to warmer temperatures, which causes more water vapor to be absorbed into the air. Warming and water absorption increase in a spiraling cycle. 

Graph showing that the energy trapped by water peaks near the equatorBased on climate variations between 2003 and 2008, the energy trapped by water vapor is shown from southern to northern latitudes, peaking near the equator.
Credit: Andrew Dessler
> Larger image
Water vapor feedback can also amplify the warming effect of other greenhouse gases, such that the warming brought about by increased carbon dioxide allows more water vapor to enter the atmosphere.

"The difference in an atmosphere with a strong water vapor feedback and one with a weak feedback is enormous," Dessler said. 

Climate models have estimated the strength of water vapor feedback, but until now the record of water vapor data was not sophisticated enough to provide a comprehensive view of at how water vapor responds to changes in Earth's surface temperature. That's because instruments on the ground and previous space-based could not measure water vapor at all altitudes in Earth's troposphere -- the layer of the atmosphere that extends from Earth's surface to about 10 miles in altitude.

AIRS is the first instrument to distinguish differences in the amount of water vapor at all altitudes within the troposphere. Using data from AIRS, the team observed how atmospheric water vapor reacted to shifts in surface temperatures between 2003 and 2008. By determining how humidity changed with surface temperature, the team could compute the average global strength of the water vapor feedback. 

“This new data set shows that as surface temperature increases, so does atmospheric humidity,” Dessler said. “Dumping greenhouse gases into the atmosphere makes the atmosphere more humid. And since water vapor is itself a greenhouse gas, the increase in humidity amplifies the warming from carbon dioxide."

Specifically, the team found that if Earth warms 1.8 degrees Fahrenheit, the associated increase in water vapor will trap an extra 2 Watts of energy per square meter (about 11 square feet).

"That number may not sound like much, but add up all of that energy over the entire Earth surface and you find that water vapor is trapping a lot of energy," Dessler said. "We now think the water vapor feedback is extraordinarily strong, capable of doubling the warming due to carbon dioxide alone."

Because the new precise observations agree with existing assessments of water vapor's impact, researchers are more confident than ever in model predictions that Earth's leading greenhouse gas will contribute to a temperature rise of a few degrees by the end of the century. 

"This study confirms that what was predicted by the models is really happening in the atmosphere," said Eric Fetzer, an atmospheric scientist who works with AIRS data at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Water vapor is the big player in the atmosphere as far as climate is concerned." 


Peter said...

You're flat-out wrong. The grey areas showing over the North Pole in (NH) winter and the South pole in (SH) winter are areas with no data coverage. Presumably the satellite used (MODIS) can't get adequate data in the dark.

You can tell it's missing data because it's pure grey rather than a shade of yellow.

Peter said...

Peter, I am not sure why you think the MODIS satellite was used.

I read the page you linked to, which hosts the animation you're looking at. I quote.

"These maps show the average amount of water vapor in a column of atmosphere in a given month. The units are given in centimeters, which is the equivalent amount of water that could be produced if all the water vapor in the column were to condense. The lowest amounts of water vapor (0 centimeters) appear in yellow, and the highest amounts (6 centimeters) appear in dark blue. Areas of missing data appear in shades of gray. The maps are based on data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA’s Aqua satellite."

Peter said...

Note also that in the second (IR) video you link in your update, there's no suggestion of an increase in humidity in the Antarctic in June.

Tenney Naumer said...

Peter, I do see that you have made some points that I should take into consideration.

I really would like to see this matter of the gray at the poles cleared up -- for one thing, the size and shape and timing of the gray areas vary from year to year, so I wonder how that would relate to satellite coverage. Note that there is a fuzzy gray ring all around Antarctica at certain times of the year. This may not be explainable by a lack of coverage.

Perhaps a inquiry sent to the maker of the animation would be in order.