Snow blow: image of Mount Everest from orbit captures enormous plume

Science News, Dec 4, 2004 by S. Perkins

Scientists are viewing a photograph of an immense plume of snow wafting from Mount Everest to learn how winds redistribute precipitation in the Himalayas and other mountain chains.

On Jan. 28, as astronauts on the International Space Station passed over Tibet, they snapped a picture of Mount Everest. The image shows a long white plume extending eastward from the peak. Knowing the distance from Mount Everest to another mountain also visible in the image, physicist Kent Moore of the University of Toronto estimates that the plume is between 15 and 20 kilometers long.

Moore dismisses the possibility that the plume was a so-called banner cloud, a type that sometimes develops on the lee side of tall peaks. Banner clouds typically form in summer months, and also weather conditions on the day the picture was taken probably wouldn't have produced a banner cloud at Mount Everest's altitude of more than 8,800 meters, he says.

It's much more likely that the plume was snow lofted from the mountain, Moore notes in the Nov. 28 Geophysical Research Letters. Satellite data indicate that between 40 and 80 centimeters of snow fell on and around Mount Everest between Jan. 22 and Jan. 25. Also, weather models suggest that winds atop the peak exceeded 50 meters per second. Winds only one-third that velocity can loft fresh snow from the ground, says Moore.

Researchers may use computer simulations of the Mount Everest plume to refine their models of blowing snow. They are working to predict how strong winds redistribute fallen snow in mountainous regions--a phenomenon that affects many scientific endeavors, ranging from estimating avalanche danger to interpreting ice cores drilled from high-altitude snowfields, according to Ana Barros, a hydrologist at Duke University in Durham, N.C.