In the middle of the Pacific Ocean, scientists are flying into bumpy air pockets near the jet stream looking for the meteorological features that cause air turbulence. The "Severe Clear Air Turbulence - Colliding with Air Traffic" (SCATCAT) project, a series of reconnaissance flights, may bring The Commerce Department's NOAA researchers closer to understanding air turbulence, a potentially dangerous phenomena that impacts aviation worldwide.

"We are taking advantage of being able to use NOAA's Gulfstream IV-SP (G-IV) jet that is flying winter storm reconnaissance missions out of Honolulu," said Mel Shapiro, Ph.D., NOAA research meteorologist and SCATCAT manager. "We want to learn why some airplanes go through regions where turbulence is expected without a problem, while others experience major upsets."

Jim Weyman, meteorologist in charge of the Honolulu Forecast Office, added, "Clear air turbulence has had major impacts on flights in and out of Hawaii. In the last few years, several flights have encountered severe turbulence resulting in significant injuries to passengers. If we can improve our knowledge of turbulence events, we will not only save lives but also thousands of dollars lost in fuel, flight rerouting, and delays."

Jack May, acting director of the Aviation Weather Center in Kansas City, Mo., welcomed the research results. "New findings from this type of research will greatly improve the forecasts of turbulence over the continental United States and large oceanic areas that the center has responsibility for and where thousands of flights everyday have the potential of encountering turbulence."

Before making a decision to fly a reconnaissance mission, conditions must be favorable for turbulence. Satellite images, aviation weather models, and air turbulence forecasts are analyzed to determine the most likely area where turbulence may develop. Upon reaching the designated research area, scientific instruments called dropsondes are ejected from the plane at high altitude. As these packages drop they send back data to the plane. This data points out areas of turbulence below the aircraft allowing the pilots to descend and purposefully fly there for the experiment. "Then we shake," said Shapiro.

Scientists are looking for two kinds of turbulence. One consists of layers of large wind changes in small vertical distances near jet streams and developing winter storm systems. The other develops when the jet stream flows over a large thunderstorm, which acts as an obstacle to the flow. In both cases, a pilot cannot tell how far the turbulence extends because it is invisible.

"To detect the fine-scale structure and layering, vertical profiles are combined with observations from the aircraft," Shapiro said. He added, "You can't build a better mousetrap without knowing how big the mouse is. Comparing the actual atmosphere to the model prediction is the key to improving aviation models that are used by commercial, civil, and military pilots for flight safety."

This year's SCATCAT mission is the third one led by NOAA and its partners: NASA, U.S. Department of Defense, Federal Aviation Administration, and the National Center for Atmospheric Research. So far, research has uncovered the following:

• Researchers have identified fine scale vertical layers 1000 feet thick, or less, in which turbulence is prevalent, helping to explain why one plane is impacted and another is not;
• Vertical waves have been discovered inside the jet stream exhibiting the character of ocean swells, which break and crash like ocean waves. Researchers are able to simulate breaking waves and incorporate the measurements into experimental forecast modeling. This new information will be used to improve operational forecasts;

The G-IV, known as NOAA's airborne meteorological workstation, is a high altitude, high-speed, twin turbofan plane that files at an altitude up to 45,000 feet in the vicinity of the jet stream, where winds may reach as high as 200 mph. The plane is conducting winter reconnaissance missions this month, but it is primarily used in surveillance flights during hurricane season to gather data on the steering flow for hurricanes to improve track forecasting. "The G-IV is NOAA's newest storm surveillance aircraft and is particularly suited for these flights because of its speed and range," said Jack Parrish, flight meteorologist and G-IV program director at NOAA's Aircraft Operations Center located at McDill Air Force Base in Tampa, Fla. Parrish is directing the winter storm mission from Honolulu. At its conclusion, the G-IV will return to Florida to gear up for the 2001 hurricane season.

Note to Editors: Media are invited to fly aboard the G-IV on a space-available basis. To arrange a flight, interview, or obtain b-roll, contact Delores Clark at (808) 532-6411.

Additional information is available on the following Web sites:
NOAA's G-IV jet: http://www.nc.noaa.gov/aoc/aircraft/givsp/givsp.html
Daily SCATCAT reports: http://www-frd.fsl.noaa.gov/mab/scatcat/dailyforecasts.html
Dropsondes: http://www.aoml.noaa.gov/hrd/nhurr97/GPSNDW.HTM