Featured Research

from universities, journals, and other organizations

Temperature Of Earth's Highest Polar Clouds Measured For The First Time

Date:
March 29, 2001
Source:
American Geophysical Union
Summary:
Scientists have for the first time obtained measurements of upper atmosphere temperatures, iron densities, and mesospheric clouds over the North and South Poles. As reported in the April 1 issue of Geophysical Research Letters, published by the American Geophysical Union, they used a sensitive lidar (radar-like laser) system, which was first deployed over Okinawa, Japan, to observe meteor trails during the 1998 Leonid meteor shower. University of Illinois researchers have now used it to probe temperatures in the upper atmosphere over both geographic poles.

Washington - Scientists have for the first time obtained measurements of upper atmosphere temperatures, iron densities, and mesospheric clouds over the North and South Poles. As reported in the April 1 issue of Geophysical Research Letters, published by the American Geophysical Union, they used a sensitive lidar (radar-like laser) system, which was first deployed over Okinawa, Japan, to observe meteor trails during the 1998 Leonid meteor shower. University of Illinois researchers have now used it to probe temperatures in the upper atmosphere over both geographic poles.

Related Articles


"Measuring temperature profiles over the poles is essential for validating global circulation models and for providing a baseline for assessing the impact of global warming over the coming decades," said team leader Chester Gardner, a professor of electrical and computer engineering. "Until now, we were limited to measurements taken with balloon-borne sensors to altitudes of less than 20 miles [32 kilometers]."

In collaboration with scientists at The Aerospace Corporation and the National Center for Atmospheric Research (NCAR), Gardner and his UI colleagues -- Professor George Papen, research scientist Xinzhao Chu, and graduate student Weilin Pan -- developed a more robust lidar system for measuring temperature profiles from the middle of the stratosphere (about 32 kilometers or 20 miles up) to the lower thermosphere at the edge of space (about 110 kilometers or 70 miles above Earth). The system uses two powerful lasers operating in the near ultraviolet region of the spectrum and two telescopes to detect the laser pulses reflected from the atmosphere.

The researchers use two techniques for determining temperature. For altitudes up to 80 kilometers [50 miles], they measure the amount of laser light reflected from air molecules to derive the temperature profile. For higher altitudes, they measure the scattering of the laser beams from iron atoms deposited in the upper atmosphere by vaporized meteors.

In June 1999, the scientists flew the lidar system over the North Pole aboard an NCAR research plane to obtain temperature and iron density measurements during the Arctic Mesopause Temperature Study. Six months later, they took the instrument to the Amundsen-Scott South Pole Station where it is now measuring the atmospheric temperature structure throughout the year. The National Science Foundation provided funding for the two measurement campaigns.

"Temperature profiles obtained in the thermosphere over the North Pole on June 21, 1999, and in the mesopause region over the South Pole on January 27, 2000, agreed closely with model predictions," Gardner said. "Significant departures from the model were observed during the austral fall, however. On May 8, 2000, for example, the lower mesosphere was about 20 degrees [Celsius; 36 degrees Fahrenheit] warmer and the upper mesosphere was about 20 degrees [Celsius; 36 degrees Fahrenheit] cooler than predicted." The mesosphere extends from the upper limit of the stratosphere, around 80 kilometers [50 miles] above sea level to the mesopause, its upper boundary. The thermosphere begins beyond the mesopause.

Gardner and his colleagues also measured the heights of polar mesospheric clouds that formed over each of the poles during mid-summer. Unlike the lower atmosphere, the upper atmosphere is colder during summer than in winter. Polar mesospheric clouds form over the summertime polar caps when temperatures fall below minus 125 degrees Celsius [-193 degrees Fahrenheit].

These clouds are the highest on Earth, forming at an altitude of about 84 kilometers [52 miles]. Their brightness and geographic extent have been increasing during the past four decades. Scientists believe that these changes may be related to increasing levels of atmospheric carbon dioxide and methane, which in the upper atmosphere lead to cooler temperatures and increasing levels of water vapor.

Surprisingly, the altitudes of the polar mesospheric clouds over the South Pole were consistently two to three kilometers [one to two miles] higher than those over the North Pole. "Higher polar mesospheric clouds may be an indication of stronger upwelling in the summer mesosphere over Antarctica compared with the North polar cap," Gardner said. "Stronger upwelling would result in a cooler mesopause region."


Story Source:

The above story is based on materials provided by American Geophysical Union. Note: Materials may be edited for content and length.


Cite This Page:

American Geophysical Union. "Temperature Of Earth's Highest Polar Clouds Measured For The First Time." ScienceDaily. ScienceDaily, 29 March 2001. <www.sciencedaily.com/releases/2001/03/010320074609.htm>.
American Geophysical Union. (2001, March 29). Temperature Of Earth's Highest Polar Clouds Measured For The First Time. ScienceDaily. Retrieved December 21, 2014 from www.sciencedaily.com/releases/2001/03/010320074609.htm
American Geophysical Union. "Temperature Of Earth's Highest Polar Clouds Measured For The First Time." ScienceDaily. www.sciencedaily.com/releases/2001/03/010320074609.htm (accessed December 21, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Sunday, December 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Lava on Track to Hit Hawaii Market

Raw: Lava on Track to Hit Hawaii Market

AP (Dec. 19, 2014) Lava from an active volcano on Hawaii's Big Island slowed slightly but stayed on track to hit a shopping center in the small town of Pahoa. (Dec. 19) Video provided by AP
Powered by NewsLook.com
Birds Might Be Better Meteorologists Than Us

Birds Might Be Better Meteorologists Than Us

Newsy (Dec. 19, 2014) A new study suggests a certain type of bird was able to sense a tornado outbreak that moved through the U.S. a day before it hit. Video provided by Newsy
Powered by NewsLook.com
Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Arctic Warming Twice As Fast As Rest Of Planet

Arctic Warming Twice As Fast As Rest Of Planet

Newsy (Dec. 18, 2014) The Arctic is warming twice as fast as the rest of the planet, thanks in part to something called feedback. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins