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Cloud Crystals

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  • jec_nobleza23
    The sharpest ever measurement of ice crystals in clouds will help to improve climate change predictions. Scientists have created an instrument designed to help
    Message 1 of 1 , Sep 1, 2008
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      The sharpest ever measurement of ice crystals in clouds will help to
      improve climate change predictions. 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.

      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 their sizes and shapes 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 greenhouse warming.

      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 the kind of ice crystals in clouds all
      the way down to the tiniest micron levels. (See the accompanying
      picture of cloud crystals; the crystals now being measured are much
      smaller than this.)

      The research team actually has built two versions of the instrument:
      one designed to operate on ground-based cloud simulation chambers or
      to operate in the fuselage of research aircraft; the other, an
      aerodynamic version that fits under the wing of the aircraft and
      measures the cloud particles directly as the aircraft flies through
      the cloud (see the accompanying picture). Neither instrument
      attempts to make a full image of the ice crystal, since this would
      suffer the same resolution limits of existing instruments. Instead
      they record the detailed pattern of scattered light from each
      individual crystal and then interpret these patterns using either
      theoretical models or by comparison with recorded patterns from
      known crystal shapes. From this data a crystal census of varying
      sizes and shapes can be made.

      "The new instruments should help map out a more complete
      understanding of complex crystal shapes found in atmospheric clouds,
      especially cirrus clouds which on any day can cover more than 20
      percent of the Earth's surface," says one of the researchers,
      Hertfordshire scientist Paul Kaye. "Our findings show that this
      optical scattering instrument could help climate modelers reduce one
      of the greatest areas of uncertainty in interpreting current weather
      trends and in making more accurate climate predictions."

      In addition, recent reports have examined the effect that pollution
      and the clouds caused by pollution have on reducing solar radiation
      reaching the ground, a development that may counterbalance global
      warming to some extent, and this new technology could help
      scientists better monitor and understand this situation.

      So far the new measurements, reported recently in the journal Optics
      Letters, have been made only in the lab, but will soon be made in
      actual clouds.
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