Unexpected Teleconnections in Noctilucent Clouds

By: Susie77 , 11:54 AM GMT on April 16, 2014

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Unexpected Teleconnections in Noctilucent Clouds


April 16, 2014: Earth's poles are separated by four oceans, six continents and more than 12,000 nautical miles.

Turns out, that's not so far apart.

New data from NASA's AIM spacecraft have revealed
"teleconnections" in Earth's atmosphere that stretch all the way from
the North Pole to the South Pole and back again, linking weather and
climate more closely than simple geography would suggest.
splash

A new ScienceCast video explores unexpected "teleconnections" in
Earth's atmosphere that link weather and climate across vast
distances.  Play it

For example, says Cora Randall, AIM science team member and Chair
of the Dept. of Atmospheric and Oceanic Sciences at the University of
Colorado, "we have found that the winter air temperature in
Indianapolis, Indiana, is well correlated with the frequency of
noctilucent clouds over Antarctica."

Noctilucent clouds, or "NLCs," are Earth's highest clouds.  They
form at the edge of space 83 km above our planet's polar regions in a
layer of the atmosphere called the mesosphere.  Seeded by "meteor
smoke," NLCs are made of tiny ice crystals that glow electric blue when
sunlight lances through their cloud-tops.

AIM was launched in 2007 to investigate these "night-shining"
clouds, to discover how they form and to learn about their inner
chemistry.  As is often the case, however, when exploring the unknown,
researchers found something they weren't even looking for:
teleconnections.

"It has been a surprise," says Hampton University professor of
atmospheric and planetary science James Russell, Principal Investigator
of the AIM mission. "Years ago when we were planning the AIM mission,
our attention was focused on a narrow layer of the atmosphere where NLCs
form.  Now we are finding out this layer manifests evidence of
long-distance connections in the atmosphere far from the NLCs
themselves."

One of these teleconnections links the Arctic stratosphere with the Antarctic mesosphere.

"Stratospheric winds over the Arctic control circulation in the
mesosphere," explains Randall. "When northern stratospheric winds slow
down, a ripple effect around the globe causes the southern mesosphere to
become warmer and drier, leading to fewer NLCs. When northern winds
pick up again, the southern mesosphere becomes colder and wetter, and
the NLCs return."
image

The winter air temperature in Indianapolis is correlated with the frequency of noctilucent clouds over Antarctica. More
This January, a time of year when southern NLCs are usually
abundant, the AIM spacecraft observed a sudden and unexpected decline in
the clouds. Interestingly, about two weeks earlier, winds in the Arctic
stratosphere were strongly perturbed, leading to a distorted polar
vortex.

"We believe that this triggered a ripple effect that led to a
decline in noctilucent clouds half-way around the world," says Laura
Holt of the University of Colorado's Laboratory for Atmospheric and
Space Physics. "This is the same polar vortex that made headlines this
winter when parts of the USA experienced crippling cold and ice."

Holt took a careful look at meteorological data and found that,
indeed, there was a statistical link between winter weather in the USA
and the decline in noctilucent clouds over Antarctica.

"We picked Indianapolis as an example, because I have family
living there," says Randall, "but the same was true of many northern
cities: cold air temperatures on the ground were correlated with NLC
frequencies high above Antarctica two weeks later," she says.

The two week delay is, apparently, how much time it takes for the
teleconnection signal to propagate through three layers of atmosphere
(the troposphere, stratosphere and mesosphere), and from pole to pole.

It is a complicated topic, but this much is clear: "NLCs are a
valuable resource for studying long-distance connections in the
atmosphere," says Russell, "and we are just getting started."

Credits:Author: Dr. Tony Phillips |  Production editor: Dr. Tony Phillips | Credit: Science@NASA

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About Susie77

Sometimes I complain about the earthly weather, but mostly I like to post about astronomy and space events. Hope you enjoy the articles.