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SDC News > SCD photo of the week: March 21, 2002

Lenticular cloud over NCAR

Lenticular clouds over Boulder

Saucers from space

Lenticular clouds over Boulder on 20 March 2002 gave the impression of a fleet of alien ships about to land.

Known meteorologically as altocumulus standing lenticularus, lenticular clouds result from strong wind flow over rugged terrain. In Colorado, jetstream winds whipping over the Rockies produce up-and-down wavelike patterns on the lee side of the Front Range. Lenticular clouds, which occur at mid-levels of the troposphere (about 20,000 feet above sea level), form at the peaks of these waves.

These eerie, elliptical cloud formations, which can also resemble stacks of pancakes, often foretell changes in the weather. Sometimes they indicate an approaching snowstorm.

For more photos of the lenticular clouds on 20 March, see those taken by Bill Randel at http://acd.ucar.edu/~randel/clouds.html . Bill is a scientist in the Atmospheric Chemistry Division at NCAR whose research interests include dynamic variability and climatology of the stratosphere and the observed variability of trace constituents in the middle atmosphere using satellite observations.

Photos: Lynda Lester

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