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 This
newsletter is a joint project of SIRS Publishing,
Inc.and the University Corporation for Atmospheric Research |
December 1993— VOLUME 1, NO. 2
ARTICLES
As travelers hustle through an airport terminal, their thoughts focus on the flight ahead. "Where is my ticket? Do I have a window seat? What will the weather be like when I land? Will I have an empty seat next to me?" After the flurry of checking in baggage, confirming seat assignments, shuffling onto the plane and placing carry-on luggage into designated compartments, travelers sink to their seats. The hard part is over. Now for the flight, which for most travelers merits little notice.
Such acceptance of the miracle of flight in a dynamic atmosphere can in part be credited to the scientists who make aviation safety a priority. The National Center for Atmospheric Research (NCAR), with support from the Federal Aviation Administration (FAA) and the National Science Foundation, and in collaboration with universities and other agencies, studies the structure and dynamics of weather that affect aviation. Scientists at the Research Applications Program (RAP) at NCAR apply their study of atmospheric dynamics to development of warning systems and forecasting capability to improve the safety of the superhighways in the sky.
Scientists and engineers work together to depict and display aviation weather hazards, such as microbursts, wind shear, gust fronts, storm motion, precipitation, and thunderstorms. Accurate prediction of atmospheric conditions allows pilots and air traffic controllers to adjust flight plans to avoid disasters and costly delays.
Adverse weather accounts for more than 40 percent of all aviation accidents. Low-altitude wind shear alone has caused approximately 650 U.S. air carrier fatalities over the past 15 years. The annual cost of U.S. air traffic delays is estimated at a minimum of $9 billion, climbing to $30 billion when passenger-related expenses are included. With worldwide traffic expected to double this decade, hazardous weather will impact aviation safety and efficiency even more.
Icing, severe thunderstorms, tornadoes, turbulence, fog, hail, heavy rain and snow, and gust fronts all threaten aircraft safety. But of all weather hazards, low-altitude wind shear has caused the most U.S. air carrier accidents. Microbursts, a dangerous form of wind shear, are produced by powerful, small-scale downdrafts of cool, heavy air that occur below thunderstorms and benign looking cumulus clouds. As the intense downdraft hits the earth's surface, the cold air shoots out horizontally, just as water from a garden hose pointed straight down gushes sideways after hitting a concrete driveway. Aircraft flying through a microburst during takeoff or landing encounter a strong headwind, followed by a downdraft, and finally a tailwind that produces an immediate, sharp loss of speed with respect to the surrounding air, and, as a result, loss of lift. Without any warning or without pilot training in recovery techniques, such a microburst encounter can be catastrophic.
Air traffic personnel at Denver's Stapleton International Airport use computer displays developed and tested by NCAR that combine information from the Low-Level Wind Shear Alert System, a network of 16 wind-speed and direction-sensing stations located at the airport, with output from the Terminal Doppler Weather Radar (TDWR). Doppler radar can detect tornadoes and major windstorms, and recently it has been used to identify low-altitude wind shear. The TDWR prototype has been operated and improved at Stapleton since 1987, and the FAA recently approved installation of 45 similar systems at major U.S. airports this decade.
The TDWR and Low-Level Wind Shear Alert System automatically feed information to air traffic controllers. For example, let's say the system detects a microburst forming over Runway 26. On the computer screen the controller sees a bright red shape superimposed on the graphic image of the runway -- this is a microburst alert. The air traffic controller scans other information about the weather on the runways, such as the intensity of the rainfall, location of any gust fronts, and predicted movement of thunderstorm cells. The controller then relays a simple message to the pilot who is approaching Runway 26: MICROBURST ALERT, 80 KNOT LOSS, 3 MILE FINAL. The pilot avoids the micro burst by executing a missed approach and landing after the short-lived hazard has dissipated.
The FAA's Aviation Weather Development Laboratory at NCAR is the center for developing and testing products than can be used to increase aviation safety. Those that show promise will be field-tested at FAA facilities. This process allows users such as air traffic controllers to gain experience and provide input to refine new systems. New weather products for aviation to be developed at NCAR may include tornado detection and forecasting, 30-minute forecasts of thunderstorm formation, regional and national turbulence detection and forecasting, ceiling and visibility forecasting, rate of snowfall forecasting and icing detection and forecasting.
Icing poses a threat to aviation safety by affecting a plane's airfoil, or aerodynamic, shape. The ice that adheres to the plane's surface increases drag and decreases lift by affecting the airflow around the plane that keeps it airborne. Like microbursts, icing is particularly dangerous during takeoff and landing, when lift and speed are critical to maintain a proper flight path off of and onto the airport runways.
Two kinds of ice build-up affect aviation safety: icing on the ground while a plane is readying for takeoff, and icing on the wings and fuselage while the plane is in the air. Wet, heavy snowfalls allow snow and ice to quickly accumulate on airplanes. Before takeoff technicians clear off the snow and deice planes with a glycol, or antifreeze solution. Then a coat of a long-chain polymer, a sticky substance that is part glycol, gets applied to the plane. The viscous nature of the polymer inhibits ice buildup and causes the snow or ice to melt. Pilots then follow a "hold-over time" data table which correlates temperature and precipitation type with the length of time a plane can safely wait on a runway before it needs another deicing treatment; pilots make the final decision on whether to take off or remain on the ground. RAP researchers are currently developing ways to improve a pilot's decision making matrix by making high resolution data on snowfall rate and short-term weather prediction more accurate. Scientists hope to accurately track snow bands so that airports know not to hold planes on the ground in locations where snow will quickly accumulate.
Once in the air, pilots monitor the aircraft for ice build-up. As a plane flies through a cloud, supercooled water droplets (below 32 degrees Fahrenheit) adhere to the plane's surface and form ice. Once a pilot detects ice on the plane either by visual inspection or feel of the aircraft, he or she can either activate heaters which melt build-up around the engine intakes, or inflate rubber tubes on the leading edges of the wings to crack away any ice. Since the conditions necessary for icing tend to be restricted to relatively shallow altitude ranges in the atmosphere, pilots can relay their icing problems to ground support and be advised as to how much higher they need to climb to get out of the icing hazard area.
Current technology allows the National Aviation Weather Advisory Unit in Kansas City, Missouri, to forecast conditions conducive to icing on a national scale, and NCAR researchers are working in collaboration with these forecasters to provide improved, and even automated, forecasts. In addition, researchers are developing technologies for airport terminal area icing detection and forecasting. Weather instruments measure dew point and temperature, and that information is combined with computer models of cloud physics. The models run algorithms (series of calculations) involving the factors in a cloud that affect icing, such as the amount of liquid water, the temperature, the size of water droplets and the availability of ice nuclei, which may act to deplete the supercooled water. The models then determine whether current information indicates a potential cloud with water droplets below 32 degrees F. Access to such technology and information allows pilots to focus on the task of flying their passengers safely.
The millions of travelers who pass through airports each year rarely consider the dangers posed to aviation by earth's dynamic atmosphere, but the y don't really need to. Through the application of basic research, organ izations like NCAR and its aviation safety program allow travelers to focus on getting to and from their assigned seats. Modern technology and the spirit of scientific innovation that made human flight possible take care of the rest.
"I didn't know what I wanted to do. I just knew I liked the weather," says Sandra Henry, an associate scientist with the Research Applications Program at the National Center for Atmospheric Research in Boulder, Colorado. Sandra always loved math and science in school, she says, so choosing a career in the sciences was not difficult.
Sandra was fortunate, she says, because she was always encouraged to pursue what she liked. "No one ever told me, 'You can't do this, or you can't be that.'" In high school she studied physics, advanced physics, chemistry, and mathematics. Mathematics was a puzzle waiting to be solved for Sandra, and she said she looked forward to working out solutions.
She actually began her undergraduate work as a civil engineering major at Colorado State University in Fort Collins, but decided the work wasn't for her after spending time doing engineering research. She strongly encourages students to try to get work and internship experiences in their field of interest, because like her, "You may do it and find, 'I don't really like this.'" She changed her major to meteorology, and earned her bachelor's degree from Metropolitan State University in Denver, Colorado. Once she focused on meteorology she interned with NCAR in several divisions, the National Weather Service, and a local television station. "At first, I didn't know what all I could do with my major, but working in various areas made it easier to decide on the exact area that I wanted to work in, which was research."
Sandra's internships paid off. After earning her master's degree in Atmospheric Science at CSU Fort Collins, she found herself back at NCAR. Including her time as a student she has been with NCAR for nine years.
As an associate scientist she studies atmospheric conditions that will enable her to predict details of thunderstorm formation. "We try to figure out exactly when and where a thunderstorm will develop." Last summer she worked with the Real-Time Analysis and Prediction of Storms project in northeastern Colorado. A specially equipped van released weather balloons to gather atmospheric data each day at around 11 a.m. Then scientists gathered at noon for a weather briefing to determine where researchers should go to find severe weather. Two cars sought out hailstorms and one car chased tornadoes. Using the data collected, the scientists hope to determine where severe weather will occur before the thunderstorms actually develop. Such predictions will be applied to aviation safety and warning systems for the population at large.
Sandra enjoys her research and encourages students to try different experiences so that they end up in a career they like. Pursuing what you want, she says, is the key to ending up where you'll be happy.
ACTIVITY
What enables some substances to remain liquid below 32 degrees Fahrenheit? How cold must other substances be before they freeze? You and your students can explore the answers to these questions with this activity.
Materials:
You will need access to a freezer, some muffin pans or ice cube trays, and a
variety of substances such as maple syrup, salt solution, honey, olive oil,
brake fluid, antifreeze, rubbing alcohol, and water. (Add to this list!)
WARNING! Do not let students ingest or inhale any substance in either of these activities. Clearly mark trays as experiments. Handle all materials carefully to avoid skin damage from frozen trays or substances.
Procedure:
Have students measure equal amounts of each substance into ice cube trays or
muffin pans and predict which ones will freeze. Label each substance clearly.
Put the trays or muffin pans into a freezer overnight. Remove the trays the
next day and note which items froze and which did not. Discuss similarities
and differences between substances that froze and those that did not. Have students
read labels to determine what properties the substances have or do not have
in common. Then have students think of other substances which they can test
against their conclusions. Pose questions about some of the substances: Why
should brake fluid not freeze? Why do we want some substances to freeze?
Icing is a serious hazard to aviation and researchers try to find substances they can use to prevent ice build-up. This activity will allow you and your students to explore substances that do and do not allow ice to stick.
Materials:
You will need ice cube trays or muffin pans, access to a freezer, water, and
a variety of substances that may or may not stick such as spray oil, Silly Putty,
Vaseline, Wet Proof for shoes, rubber cement, clay, Teflon, ski wax, car wax,
and water-proofing spray.
Procedure:
Have students coat the insides of the muffin pans with each of the substances
and label each one. Leave one muffin holder uncoated as a control. Have students
predict which substances ice will stick to. Fill each muffin pan with water,
label the substances clearly, and put the tray in a freezer overnight. (Toothpicks
will allow the ice to be removed more easily.) Check to see which 46 ice muffins"
will pull right out without bringing the substance, and which ones have stuck
to the substance. Have students read labels to determine what properties the
substances have or do not have in common. Then have them think of other substances
they can test against their conclusions.
Teachers: We want to hear your results and what other substances your classes tested. Send or e-mail (chanson @ncar.ucar.edu) your results and we will share them with anyone who requests them.
RESOURCES
The National Center for Atmospheric Research, with the support of the National Science Foundation, developed an interactive exhibit about microbursts and thunderstorms. Two copies will be displayed at airports and science centers around the country through 1996. The exhibit will make an excellent enrichment field trip after a study of weather and aviation safety. The Preliminary 1994 schedule follows:
Nov. 13, 1993 - Jan. 9, 1994
American Museum of Science and Energy
Oak Ridge, TN
615-576-6024
Jan. 15 - March 13,1994
Douglas Int'l Airport
Charlotte, NC
704-359-4000
Jan. 29 - June 12, 1994
Carnegie Science Center
Pittsburgh, PA
412-237-3400
April 2 - July 10, 1994
Dallas/Ft. Worth Int'l Airport
Dallas, TX
214-574-8080
July 2 - Aug. 28, 1994
Science Spectrum
Lubbock, TX
806-797-1676
Oct. 22, 1994 - Jan. 2, 1995
Kansas City Int'l Airport
Kansas City, MO
816-471-0077
Dec. 3, 1994 - Jan. 29, 1995
Rochester Museum and Science Center
Rochester, NY
716-271-4320
Please write to Thunderstorm Detectives, c/o NCAR, P.O. Box 3000, Boulder, CO 80307 for a 1995 exhibit location calendar.
Thunderstorm Detectives Poster
If you would like a copy of the Thunderstorm Detectives educational poster which
features a spectacular four-color photograph, student activities, and general
storm information, please send a check for $4 to cover postage and handling
to: NCAR Thunderstorm Detectives, c/o Caroline Hanson, P.O. Box 3000, Boulder,
CO 80307-3000.
SIRS offers a variety of resources for the study of weather and aviation safety.
Perfect for libraries and classrooms, SIRS Photo Essays are a series of posters which "tell a story." Each Photo Essay unit consists of eight posters focused on an issue or concept. Along with the photographs and brief text, most units include maps, charts, graphs and other graphic elements to put the topic in context and promote visual literacy. Photo Essays can be arranged on bulletin boards or any wall space, or used in classroom discussions.
Among the 20 Photo Essay units, several pertain to the topics discussed in this issue of Science Now. "Weather," "Hurricanes and Tornadoes," "Global Warming" and "Ozone Depletion" are units that focus on various conditions which affect our atmosphere and daily lives. Students can learn how the rising level of "greenhouse gases" affect climate, how modem technology is used to accurately forecast weather, and how tornadoes are formed. Graphic drawings accurately depict the inside of the hurricane, the greenhouse effect and the weakened ozone shield.
Posters measure 11" x 14" and are laminated for long-time use. Each unit includes a study guide with bibliographies and worksheets to help users analyze the topics. Catalog cards are included.
Other resources available to further study the effect of weather on aviation safety are "Earth Science" and "Applied Science" volumes from the five-volume SIRS Science Series; and "The Atmosphere Crisis," "Transportation" and "Technology" volumes from SIRS 34-volume Critical Issues and Social Issues Series. Based on the premise that many outstanding articles are irretrievable soon after publication, SIRS research staff selects articles from national and international newspapers, magazines, government publications and journals, and structures them for reference use. SIRS articles are reproduced both in print and CD-ROM formats.
For more information on SIRS Photo Essays and SIRS Science Series, please contact SIRS Customer Service at 1-800-232-SIRS (8:30 a.m. to 5:00 p.m. Eastern Time), or via e-mail at custserve@sirs.com.
Science
Now
is jointly published by the Walter
Orr Roberts Institute at the University
Corporation for Atmospheric Research
and SIRS Publishing, Inc.
(Social Issues Resources Series.) Science
Now is published three times during the
school year and is distributed to SIRS subscribers.
Comments and questions should be directed
to Joyce Gellhorn via Internet at jgellhorn@sprynet.com.
You can also contact your SIRS representative
or write to:
SIRS Publishing, Inc.
P.O. Box 272348
Boca Raton, FL 33427-2348
http://www.sirs.com
Editor:
Caroline Hanson
Scientific
Editor:
Pat Kennedy
Contributors:
Bob Henson, NCAR Outreach and Information Staff;
John McCarthy, Director of the Research Applications Program;
Marcia Politovich, Sandra Henry, RAP
UCAR is a consortium of over 60 universities in the U.S. and Canada with doctoral programs in atmospheric and related sciences. UCAR manages and operates the National Center for Atmospheric Research under the sponsorship of the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Anyone who undertakes any of the activities described herein shall do so at their own risk; UCAR and SIRS Publishing, Inc. assume no liability, whatsoever, for any injury or harm, which may result therefrom.
© COPYRIGHT 1993 UNIVERSITY CORPORATION FOR ATMOSPHERIC RESEARCH. ALL RIGHTS RESERVED.
Note to Teachers: Permission is hereby granted to copy all or any portion of this publication for distribution to third parties provided such copying and distribution occur for the benefit of research, scientific and educational purposes and for no other purposes including, but not limited to, commercial exploitation purposes. In the event copying occurs or derivative works, as defined under U.S. Copyright Laws, are created, all notices and/or credits recited herein must remain intact on any copies made or derivative works created.