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Scientists Studying Wintry Ice in Summer Clouds

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  • Sonya
    NASA/Goddard Space Flight Center--EOS Project Science Office 31.01.2005 Scientists Studying Wintry Ice in Summer Clouds Known to interrupt hot summer
    Message 1 of 2 , Feb 1, 2005
      NASA/Goddard Space Flight Center--EOS Project Science Office 31.01.2005

      Scientists Studying Wintry Ice in Summer Clouds

      Known to interrupt hot summer afternoons with almost daily
      thunderstorms, convective cloud systems are very common in Florida. This
      image shows the unique shape of these systems, often called an "anvil"
      because of their potential to grow quite wide at the top and bottom,
      remaining narrow in the middle. Image credit: NOAA

      Clouds, particularly the high thin cirrus clouds, play a major role in
      the balance of (reflecting and absorbing) solar energy between the Earth
      and space. Scientists are trying to find out more about the ice crystals
      within the cirrus clouds and what role they play in this balance. Image
      credit: NASA

      Winter is here, snow is falling in many areas of the country, and some
      of us are already wishing for the return of hot summer days. But, would
      you believe that even on the hottest summer day the temperature inside
      some clouds remains icy and winter-like, producing temperature readings
      as cold as negative 70 degrees Celsius (negative 94 degrees Fahrenheit)?
      Would you also believe that the ice crystals that form at the top of big
      summertime clouds may help scientists predict next winter's snowstorm?

      Last month, scientists from NASA's Langley Research Center in Hampton,
      Va. and Goddard Space Flight Center in Greenbelt, Md. published a paper
      in the Journal of Geophysical Research on the importance of classifying
      ice crystals within the big summertime clouds, or convective cloud
      systems, as observed during a Florida-based research campaign. In their
      paper, the scientists showed that their instruments can identify the ice
      crystals and now they can begin to classify the crystals. By learning to
      classify the ice crystals in clouds, these scientists hope to contribute
      to improving weather and climate models, the complex computer programs
      used to show future atmospheric conditions.

      Weather and climate computer models are complex because they must
      account for hundreds of variables, including many that seem completely
      unpredictable. Vincent Noel, a research scientist with Analytical
      Services and Materials at NASA Langley and the author of the journal
      article, explains, "Usually climate prediction means predicting the
      evolution of temperature, pressure, relative humidity, and plenty of
      other variables, over small (a few days) and large (a few centuries)
      timeframes. However, to predict all this stuff with enough accuracy, we
      need to take into account clouds -- and for the time being, clouds are
      the most important source of uncertainty in climate prediction."

      Recognizing that clouds represent so much scientific uncertainty, some
      NASA scientists and other researchers decided to study tropical
      convective clouds in Florida, a type of large cloud system very common
      in that area. Their research project, called CRYSTAL-FACE (Cirrus
      Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus
      Experiment), took place in the summer of 2002 throughout the state of
      Florida and the Gulf of Mexico, with the immediate goal of studying all
      aspects of the unique convection cloud formations from aircraft, land
      and satellite-based instruments.

      If you have spent a day at Disney World in Orlando, or if you have
      relaxed on the beaches of South Florida, you have likely seen convective
      or heat-generated clouds. These clouds form when the Sun's rays warm the
      ground, causing hot air to rise, and condense into clouds. They are
      unique because they are massive in size, at times ranging from 100 to
      200 km wide (62 to 124 miles); they form and dissipate very quickly, in
      as little as two hours; and they can be extremely thick, reaching 15 km
      (9.3 miles) in height, which is 6 km (3.7 miles) taller than Mt. Everest.

      At the top of the convective clouds are cirrus clouds made of ice
      crystals. These crystals effect weather and climate in two ways: first,
      depending on the ice crystal's shape, it affects the amount of Sun's
      energy reflected or trapped near Earth's surface; and second, in their
      relationship with ozone destruction in the upper atmosphere (stratosphere).

      "Because of all this solar radiation, the Earth gets hot," said Noel.
      "When any body is hot, it radiates infrared light." Infrared is light at
      one end of the spectrum, and people use infrared goggles to see things
      in the dark (which is how you can see people in the dark using infrared
      goggles). "Clouds trap this infrared radiation, absorb it, and re-emit
      it later; this is called the greenhouse effect." Clouds, specifically
      cirrus clouds, are the reason that a lot of infrared radiation stays
      near Earth instead of going into space.

      Because of their high altitude, ice clouds touch the tropopause, the
      region between the troposphere (the atmospheric layer closest to Earth)
      and the stratosphere. When the rising air on a summer day is hot enough,
      it can move fast enough where it "punches through" the tropopause and
      into the stratosphere. This "overshooting cloud top" brings water vapor
      into that layer of the upper atmosphere, where it contributes to
      destroying the "good ozone" that protects us from the Sun's harmful
      ultraviolet (UV) radiation.

      Then the ozone reacts with the UV radiation, and creates oxygen again.
      This cycle results in less UV radiation getting to Earth. Unfortunately,
      water can also react with ozone, thus destroying the ozone faster than
      it is created. "So, if there's too much stratospheric water, the
      creation/destruction cycle of ozone is affected," said Noel.

      The size, shape and composition of the ice crystals may reveal a lot
      about their effects on these atmospheric processes. "The ice crystal
      shapes are infinite and varied. We don't know which shapes are dominant,
      a problem when trying to predict climate change because the shape
      influences the quantity of sunlight reflected back into space," said Noel.

      The scientists used short pulses of laser light known as Lidar, to
      classify ice crystals. They compared Lidar measurements from high-flying
      aircraft (up to approximately 20 km, or 12.4 miles) with measurements
      from other instruments. In the future, they hope to use satellite data
      to get the information, instead of flying airplanes.

      One upcoming long-term study that will use a space-based instrument is
      the CALIPSO satellite mission (Cloud-Aerosol Lidar and Infrared
      Pathfinder Satellite Observations). CALIPSO is scheduled to be launched
      in June 2005, and will give us new, never-before-seen 3-D perspectives
      of how clouds and aerosols form, evolve and affect Earth's weather,
      climate and air quality.


      More information: www.nasa.gov/centers/langley/science/ice_crystals.html
      www.larc.nasa.gov


      ---------------------
      Sonya PLoS Medicine
      The open-access general medical journal from the Public Library of Science
      Inaugural issue: Autumn 2004 Share your discoveries with the world.
      http://www.plosmedicine.org



      [Non-text portions of this message have been removed]
    • Pat Neuman
      ... NASA/Goddard Space Flight Center--EOS Project Science Office 31.01.2005 Scientists Studying Wintry Ice in Summer Clouds Excerpt: ... Because of their high
      Message 2 of 2 , Feb 8, 2005
        --- 01 Feb 2005: In Paleontology_and_Climate - Sonya -
        NASA/Goddard Space Flight Center--EOS Project Science Office
        31.01.2005
        Scientists Studying Wintry Ice in Summer Clouds

        Excerpt:

        ... Because of their high altitude, ice clouds touch the tropopause,
        the region between the troposphere (the atmospheric layer closest to
        Earth) and the stratosphere. When the rising air on a summer day is
        hot enough, it can move fast enough where it "punches through" the
        tropopause and into the stratosphere. This "overshooting cloud top"
        brings water vapor into that layer of the upper atmosphere, where it
        contributes to destroying the "good ozone" that protects us from the
        Sun's harmful ultraviolet (UV) radiation. ...
        http://groups.yahoo.com/group/Paleontology_and_Climate/message/11766
        More
        http://www.nasa.gov/centers/langley/science/ice_crystals.html
        http://www.larc.nasa.gov


        Pat N
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