Saturday, July 19, 2008

Sharpest measurement of ice crystals in clouds ever will help in climate modeling

Science Daily: Scientists have created an instrument designed to help determine the shapes and sizes of tiny ice crystals typical of those found in high-altitude clouds, down to the micron level (comparable to the tiniest cells in the human body), according to a new study. The data produced using this instrument likely will help improve computer models used to predict climate change.

Among the hundreds of factors climate scientists must take into account in modeling weather, the nature of clouds is one of the most important and least understood. The best researchers could do in the past to measure cloud ice crystals was to try to record images of them, but for crystals below 25 microns, the images were too blurred to allow accurate determination of the crystal's shape.

Researchers need to know the shape and sizes of these ice crystals because these properties influence how much incoming sunlight gets absorbed in the atmosphere and how much gets reflected right back out into space. This, in turn, can have a huge impact on the magnitude of possible global warming or cooling.

Now scientists from the University of Hertfordshire and the University of Manchester in the United Kingdom and Colorado State University in the United States have developed an optical scattering instrument that can evaluate the size of the crystals in a different way. Using this instrument, the researchers have been able to determine sizes and shapes of cloud ice crystals all the way down to the tiniest micron levels….

Microscope image of an ice crystal (diamond dust) sampled from the air in a height of 3000 meters above the Antarctic ice sheet. Red lines show light refraction of 22° producing a halo around the sun. Shot by Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research, Wikimedia Commons, under the Creative Commons Attribution ShareAlike 2.5 License

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