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Scientists Delve into the Icy Hearts of Hurricanes(Images available at: ftp://ftp.ucar.edu/communications) Despite its tropical origin, the upper two-thirds of a typical hurricane is made up largely of ice. This month scientists from the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, are bringing unique cloudprofiling instruments into this mysterious upper realm in a project to help improve hurricane forecasting and modeling. Supporting NCAR's participation are the National Science Foundation (NSF) and NASA. CAMEX-4, the fourth Convection And Moisture Experiment (CAMEX), is the first of its kind for the U.S. Weather Research Program (USWRP), a multi-agency effort to reduce the destructive impact nationwide of disastrous weather, particularly hurricanes. Scientists aboard NASA's DC-8 and ER-2 research aircraft homebased at Jacksonville (Fla.) Naval Air Station will join satellites and other sensors to analyze the structure and impact of hurricanes at sea and as they hit land. The project runs from August 16 to 24 September. "CAMEX addresses one of the most challenging forecast problems, hurricane landfall," says Cliff Jacobs, program director in NSF's division of atmospheric sciences, which is funding the research. "This experiment is particularly important because of the collaboration on a high priority research area of the interagency USWRP." NCAR's Andrew Heymsfield, one of the principal investigators, will fly seven instruments aboard the DC-8 to get the clearest-ever picture of frozen and condensed water within a hurricane. "A hurricane might extend 60,000 feet high, but only the bottom 15,000 feet is in the rain phase. The upper 45,000 feet or so is usually ice particles," explains Heymsfield, "and that's what we're going to be looking at." The huge swirls of white cloud evident on hurricane satellite photos consist mainly of ice crystals. As water vapor freezes to form ice, it releases vast amounts of latent heat, which "helps to drive hurricanes," Heymsfield says. "You need to get the ice phase going to really intensify the hurricane." Typical hurricane-hunting flights operate below 20,000 feet, so they obtain only limited information on ice content. Heymsfield's instruments will fly as high as 43,000 feet aboard the DC-8. A sophisticated cloud particle imager shines a tiny laser beam on an array of photo diodes. Ice crystals passing in front of the laser leave a shadow on the array. The resulting photos, taken 40 times each second, show the crystal structure in fine detail. Heymsfield has taken the imager into cirrus clouds, but this will be its first foray into a hurricane. With the help of other sensors that measure overall moisture, Heymsfield and colleagues will study how much water a hurricane deposits in its upper levels and how much dry air it pulls down into the calm, clear eye. "For better forecasts of hurricane landfall and intensification, we need to know how much ice is transported into the upper two-thirds of a hurricane," says Heymsfield.
NSF is an independent federal agency which supports fundamental research and education across all fields of science and engineering, with an annual budget of about $4.5 billion. NSF funds reach all 50 states, through grants to about 1,800 universities and institutions nationwide. Each year, NSF receives about 30,000 competitive requests for funding, and makes about 10,000 new funding awards.
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