Can Doppler Weather Radar Detect Turbulence? Three Aircraft Head In To Colorado Storms To Find Out

The Colorado turbulence research experiment is part of the NationalAeronautics and Space Administration's Aviation Safety Program. Otherpartners are the National Science Foundation (NSF), AlliedSignal,Rockwell Collins, Colorado State University, and the South Dakota Schoolof Mines and Technology. NSF is NCAR's primary sponsor.

AlliedSignal will test its airborne weather radar aboard a company-ownedConvair 580 while Rockwell-Collins tests its own similar radar aboardits Sabreliner. Both planes will record the aircraft's response toturbulence, such as accelerations and attitudes. An armored T-28 storm-penetration aircraft operated by the South Dakota School of Mines andTechnology will gather both atmospheric and airplane-response data as itflies into the storm ahead of the other two. Its pilot will report onlightning, hail, and turbulence to the Convair and Sabreliner pilots asthe three search for pockets of turbulence while skirting areas of heavyrain and hail. All three planes will fly nearly every afternoon thatstorms and turbulence are present.

On the ground, Colorado State University will operate two Doppler radarsto locate storms and verify aircraft data. CSU researchers and theirNSF-sponsored summer students will gather the ground radar data fromsites near Greeley and the Pawnee National Grassland. Sounding balloonslaunched from NCAR's mobile weather van will measure temperature,pressure, humidity, and winds.

NCAR atmospheric scientist Larry Cornman will guide daily operations.Says Cornman, "Airborne Doppler radar is a promising tool for detectingconvective turbulence. If everything goes well, it could be ready foruse by U.S. airlines within two years." Onboard Doppler radars arealready detecting low-level wind shear from commercial planes. Cornmanwill develop the mathematical equations that will make the standardweather radar data useful for detecting convective turbulence.

Convective turbulence is associated with storms and clouds. It can ripsections off small planes and injure crew and passengers aboard largercraft. Up to 60% of aircraft encounters with turbulence is due toturbulence associated with thunderstorms. Poor forecasting and detectionof all kinds of turbulence cost U.S. airlines $100 million each year ininjuries and disrupted operations.

Convective turbulence may be detected by weather radars that bounceradio waves off large raindrops, snowflakes, and hailstones. To detectclear-air turbulence, which occurs in the absence of clouds, scientistshave experimented with lidars, which reflect laser beams off tiny movingparticles invisible to the radar.

In 1996 the White House established a Commission on Aviation Safety andSecurity. As a result, the Federal Aviation Administration and NASAAviation Safety Programs were instituted. One element of these safetyprograms is reduction of injuries from aircraft encounters withatmospheric turbulence.

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

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Note to Editors: Reporters may fly on AlliedSignal's Convair 580 on aspace-available basis. Flights will be decided at a noon weatherbriefing on the same day.

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