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NYTimes article on strikes and ice

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  • Mike Doran
    http://www.nytimes.com/aponline/science/AP-Fire-and-Ice.html Report: Icier Clouds Make More Lightning E-Mail This Printer-Friendly By THE ASSOCIATED PRESS
    Message 1 of 1 , Aug 11, 2005
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      http://www.nytimes.com/aponline/science/AP-Fire-and-Ice.html


      Report: Icier Clouds Make More Lightning
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      By THE ASSOCIATED PRESS
      Published: August 11, 2005
      Filed at 7:27 p.m. ET

      WASHINGTON (AP) -- Poet Robert Frost once pondered whether the world
      would end in fire or in ice. Weather researchers say where you find
      ice you find fire -- at least in the form of lightning.

      Whether the storm was over land, ocean or coastal areas, clouds with
      more ice produced more lightning, researchers studying satellite
      radar images report in the journal Geophysical Research Letters.

      ''The new thing is that when you look at different areas of the
      planet ... the hypothesis about the importance of ice holds up,''
      Walter A. Petersen of the University of Alabama at Huntsville said
      Thursday.

      He said weather scientists have known there was a relationship
      between ice and lightning, but were learning new details by studying
      the National Aeronautics and Space Administration satellite images
      which can look at both the number of lightning strikes and the volume
      of ice in a cloud at the same time.

      Crucial is what is called precipitation-sized ice, particles of a
      millimeter or so which sometimes can be seen falling as small
      hail. ''Where you have more of that, you tend to have more
      lightning,'' Petersen said.

      These particles crash into smaller ice particles in the swirling
      winds inside storm clouds, resulting in a separation of electrical
      charge.

      The charge separated between smaller and larger particles, with the
      smaller carrying a positive charge to the top of the thundercloud and
      the larger ones with the negative charge sinking to the bottom, he
      explained in a telephone interview.

      ''You effectively make a big battery with positive and negative
      ends,'' he said, with the charge building up until it is discharged
      as lightning.

      The relationship between ice volume and lightning held true over such
      varied locations as the Himalaya Mountains, Central Africa,
      Madagascar, northern Australia and Florida, the researchers reported.

      They found small areas of subtropical South America where lightning
      flash density seemed slightly less than would have been expected for
      the measured ice amount. Since they could find no physical reason for
      this the researchers said it may be a sampling error. They are doing
      more research on those areas.

      The work was funded by the NASA's Earth Observing System and Earth
      Science Enterprise programs.

      ^------

      On the Net:

      Geophysical Research Letters: www.agu.org/journals/gl/
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