NCAR Press Release #1994-6 For Release until March 25, 1994 Contact: Joan Vandiver Frisch Manager, NCAR Media Relations Boulder, CO 80307-3000 Tel. 303-497-8607; Fax: 8610 E-mail: jfrisch@ncar.ucar.edu NCAR, NOAA and University Scientists Search for Clues to Aircraft Icing at and near Denver's Stapleton Airport BOULDER--While spring may be right around the corner, Colorado scientists are in the midst of a major study on aircraft icing. During a two-month field program under way until March 25, researchers with the National Center for Atmospheric Research (NCAR) in Boulder, Colorado (sponsored by the National Science Foundation, or NSF), in cooperation with other federal and university scientists, are searching for the secrets that cause supercooled water droplets and ice crystals to form in clouds. This research is sponsored by NSF through an Interagency Agreement in response to requirements and funding by the Federal Aviation Administration's Aviation Weather Development Program. United Air Lines ground operations at Stapleton International Airport in Denver is also cooperating with studies designed to improve forecasting for ground de-icing efforts. Tiny water droplets, suspended in air below 32ˇF, freeze almost instantly when they encounter a hard surface, such as an airplane, causing ice to build upon its body and wings. To better predict aircraft icing, meteorologists need to better understand important factors leading to its cause--supercooled water droplets. Though icing conditions can be very localized, standard icing forecasts are so general (often covering entire states) that they can be of little help in fine- tuning flight plans. Led by operations codirectors Marcia Politovich and Roy Rasmussen, both of NCAR, approximately 25 scientists are examining in-cloud ice as part of a multiyear study based at NCAR. The Winter Icing and Storms Project (WISP) 1994 is using four radars, two airplanes, and an array of surface and airborne sensors to sample clouds along ColoradoŐs Front Range from January 25 to March 25. Now in its fourth winter field program, the study has advanced understanding of how regions of supercooled water develop and evolve. Ironically, the worst icing conditions for aircraft can occur in a shallow cloud deck that may not contain ice itself, or produce any rain or snow at the ground, but is full of supercooled water. Since ice crystals aloft can reduce the icing threat to an airplane by depleting supercooled cloud drops, this yearŐs study is focusing on the origins of in-cloud ice. A number of innovative instruments will sample clouds from aboard the University of Wyoming King Air and the NSF/NCAR four-engine Electra research aircraft. For example, air samples taken from just outside ice-bearing clouds will be rushed to a cloud chamber at Colorado State University, where scientists will try to recreate the ice-production process that the air would have encountered within the cloud. Researchers will work to connect these small-scale observations to large-scale weather, so that future forecasts can predict how much a given cloud or storm might threaten aircraft. This could eventually result in more direct routing, lower fuel costs, and safer flights for the public. The WISP participants are working with operational aviation weather forecasters at the National Weather Service's National Aviation Weather Advisory Unit at Kansas City to transfer the icing forecast technology being developed. As a result of this cooperative effort, the techniques developed through this winter's research will be available for operational use next winter in support of aviation. Besides NCAR, WISP participants include Colorado State University, the Universities of Illinois and Wisconsin, the University of Nevada's Desert Research Institute, Yale University, and the National Oceanic and Atmospheric Administration's Environ-mental Technology and Forecast Systems laboratories. NCAR is sponsored by NSF and managed by the University Corporation for Atmospheric Research, a consortium of 61 universities with Ph.D. programs in the atmospheric or related sciences. Writer: Bob Henson NOTE: The media is invited to visit the operations control center at NCAR. Contact Joan Frisch, NCAR Media Relations, 303-497-8607.