Scientists Probe the Jet Stream for Clues to Clear Air Turbulence

BOULDER -- Through early February, a team of scientists is sending probes into the jet stream over the Pacific Ocean to learn more about clear air turbulence. Research aircraft are dropping instruments over portions of the ocean to improve forecasts of weather systems and provide insight into the sudden, invisible gusts that pose an extreme hazard to aircraft. The program is a collaborative effort between the National Center for Atmospheric Research (NCAR), the National Oceanic and Atmospheric Administration (NOAA), the Federal Aviation Administration, and the Naval Research Laboratory (NRL) in Monterey, California. NCAR's primary sponsor is the National Science Foundation.

Commercial pilots flying east take advantage of the fast-moving winds at about 35,000 feet, in the jet stream's central core, to gain extra momentum. However, this puts them at risk for clear air turbulence. Twenty passengers aboard a Japanese airliner were injured on January 20 as the aircraft was struck by severe turbulence above the northwest Pacific just east of Japan. Scientists want to understand why some jet streams produce severe turbulence and others do not. "The idea is to examine the core's structure to see what role it might be playing in clear air turbulence," says NCAR scientist Robert Gall.

The special observations of turbulence are piggybacking onto the Winter Storm Reconnaissance flights being sponsored by NOAA's National Weather Service (NWS) in cooperation with the NOAA Aircraft Operations Center and the U.S. Air Force Reserves. Researchers are planning two dedicated missions with the NOAA G-IV aircraft from Honolulu between January 16 and February 15, in addition to the Winter Storm Reconnaissance flights.

Dropwindsondes deployed into turbulent areas of the jet stream will provide data on the structure of the jet stream between 27,000 and 45,000 feet, the flight altitude of major airlines. The project's data will be used to verify experimental turbulence prediction models at NCAR, NOAA, and NRL and to learn how operational NWS forecast models might be improved to give pilots more accurate warnings of turbulence.

NCAR is managed by the University Corporation for Atmospheric Research, a consortium of more than 60 universities offering Ph.D.s in atmospheric and related sciences.