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NCAR News Release

2001-22 FOR IMMEDIATE RELEASE: August 13, 2001

NCAR Scientists Delve into the Icy Hearts of Hurricanes

David Hosansky
UCAR Communications
P.O. Box 3000
Boulder, CO 80307-3000
Telephone: (303) 497-8611
Fax: (303) 497-8610
E-mail: hosansky@ucar.edu

BOULDER -- Despite its tropical origin, the upper two-thirds of a typical hurricane is largely ice. Scientists from the National Center for Atmospheric Research (NCAR) are bringing unique cloud-profiling instruments into this mysterious realm in a NASA-sponsored project to help improve hurricane forecasting and modeling. Also supporting NCAR's participation is the National Science Foundation, NCAR's primary sponsor.

Based at Florida's Jacksonville Naval Air Station, the project runs from August 16 to September 24. NASA's DC-8 and ER-2 research aircraft will join satellites and other sensors to analyze the structure of hurricanes at sea and as they hit land.

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. One is a sophisticated cloud particle imager that 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 a 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.

The project will also gain unprecendented detail on winds near the tops of hurricanes. Flying as high as 65,000 to 70,000 feet, the ER-2 will launch GPS dropsondes, NCAR-designed instrument packages that use the Global Positioning System. As they parachute down, the dropsondes will gather wind, temperature, and moisture data at upper levels about every 50 to 100 feet. The GPS dropsondes -- never before released at these heights -- will be launched from a new automated deployment system developed at NCAR. As many as ten DC-8 and ER-2 flights will take place, depending on where and when hurricanes develop. The aircraft range of more than 1,700 miles encompasses the entire Gulf of Mexico, most of the Caribbean Sea, and much of the western Atlantic. If the Atlantic season is unusually quiet, the aircraft may venture into the Pacific.

CAMEX-4, the fourth Convection and Moisture Experiment, is the first field project of the U.S. Weather Research Program, a multiagency effort to reduce the national impact of disastrous weather, particularly hurricanes. NCAR's Robert Gall is the USWRP's lead scientist. CAMEX is sponsored by NASA's Earth Science Enterprise. NCAR is managed by the University Corporation for Atmospheric Research, a consortium of 66 universities offering Ph.D.s in atmospheric and related sciences.

About High-Resolution Images and Video:

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video: camex.qt (6 Mb, Requires free QuickTime Player)

In this two-minute video, NCAR scientist Andrew Heymsfield describes his CAMEX-4 research on ice crystals within hurricanes.

high resolution image: hurrpic.tif (832 x 660, 543 Kb)

This satellite photo of 1998's Hurricane Mitch shows the vast sheets of ice-crystal cloud extending outward at high levels. (Courtesy NASA-GSFC, data from NOAA GOES.)

high resolution image: cpi.tif (1232 x 704, 852 Kb)

NCAR is using a cloud particle imager developed with Spec Inc. to study ice crystals at upper levels inside hurricanes. These crystals, ranging from 400 to 600 microns (millionths of a meter) in diameter, were profiled inside an Oklahoma cirrus cloud. The structure of ice crystals may shed light on important processes in hurricane evolution.

-The End-

Writer: Bob Henson

Note to Editors: CAMEX media day is August 16, with a news conference scheduled for 9:00 a.m. in the conference room of Building 1, Jacksonville Naval Air Station. For details, contact Steve Roy, NASA, 256-651-4712 (cell) or 1-800-821-9641 (pager).

On the Web:
CAMEX-4 home page

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The National Center for Atmospheric Research and UCAR Office of Programs are operated by UCAR under the sponsorship of the National Science Foundation and other agencies. Opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any of UCAR's sponsors. UCAR is an Equal Opportunity/Affirmative Action employer.

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