This image of Polar Mesospheric Clouds (PMC) from the Aeronomy of Ice in the Mesosphere Cloud Imaging and Particle Size (AIM-CIPS) instrument on July 14, 2009 in the northern polar region. The North Pole (90N) is in the center. Latitude bands of 80N, 70N, and 60N are also indicated by the light blue circles. (Credit: NASA)

ScienceDaily (Dec. 16, 2009) — NASA's Aeronomy of Ice in the Mesosphere (AIM) satellite has captured five complete polar seasons of noctilucent (NLC) or "night-shining" clouds with an unprecedented horizontal resolution of 3 miles by 3 miles. Results show that the cloud season turns on and off like a "geophysical light bulb" and they reveal evidence that high altitude mesospheric "weather" may follow similar patterns as our ever-changing weather near the Earth's surface.

These findings were unveiled today at the Fall Meeting of the American Geophysical Union today in San Francisco.

The AIM measurements have provided the first comprehensive global-scale view of the complex life cycle of these clouds, also called Polar Mesospheric Clouds (PMCs), over three entire Northern Hemisphere and two Southern Hemisphere seasons revealing more about their formation, frequency and brightness and why they appear to be occurring at lower latitudes than ever before.

"The AIM findings have altered our previous understanding of why PMCs form and vary," stated AIM principal investigator Dr. James Russell III of Hampton University in Hampton, Va. "We have captured the brightest clouds ever observed and they display large variations in size and structure signifying a great sensitivity to the environment in which the clouds form. The cloud season abruptly turns on and off going from no clouds to near complete coverage in a matter of days with the reverse pattern occurring at the season end."

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