smooth ride to Juneau:
RAP maps wind shear and turbulence at isolated airport
That ubiquitous air travel safety announcement about fastening
seatbelts and placing seats in their upright positions has a special meaning
when it comes to flying into Juneau International Airport. The local wind
shear and turbulence are notorious because the mountains that tightly
encircle the airport produce a complex wind-flow pattern that literally
rattles passengers who travel in and out of Alaskas small capital
Two airplanesa University of Wyoming King Air
and an Alaska Airlines 737-400gather data on RAPs prototype
As the project manager for the FAA-sponsored Juneau Wind Project, Bob
Barron of the Research Applications Program hopes to give travelers a
smoother, safer ride.
Bob and his colleagues are developing a prototype warning system that
issues up-to-the-minute alerts about wind shear and turbulence to air
traffic controllers, airline dispatchers, and pilots. The goal is to warn
pilots in time to prevent injuries to passengers and crew. RAP designed
a similar system thats operating at Hong Kongs Chek Lap Kok
Its great that NCAR can use its scientific and technical
expertise to contribute to society on this day-to-day operational level,
RAPs Bob Barron and Deirdre Garvey.
The RAP team used anemometers and wind profilers to set up the Juneau
warning system. The devices use vector mathematics to create a comprehensive
picture of surrounding winds and to determine the danger these winds pose
to airplanes and passengers.
A wind profiler is an upward-looking radar that can measure turbulence,
wind speed, and wind direction. It gives researchers a profile of horizontal
winds and turbulence at 60-meter (200-foot) increments up to about 2.5
kilometers (1.5 miles). An anemometer also measures wind speed and wind
direction, but its measurements are at a single point near the ground.
The team placed the anemometers and wind profilers at a variety of locations
ranging from the airports runways to the surrounding mountains.
Many sites were chosen for their proximity to flight paths, while others
were placed upstream to monitor incoming air before it reaches the airport.
RAP is working with the Atmospheric Technology Division to locate and
operate the instruments. From 1996 to 1997, ATD collected wind data for
several months to explore wind patterns and ultimately determine the best
locations for the wind profilers in Juneau. ATDs Steve Cohn has
helped ensure the accuracy and proper functioning of the Juneau wind profilers,
analyzing data with RAPs Steve Mueller, Andrew Weekley, Cory Morse,
and Kent Goodrich.
By boat or plane
Despite a population of barely more than 30,000, Juneau has a busy airport.
This is because, unlike Rome, no roads lead to Juneau. The only ways in
or out are by boat or plane. From apples to zucchini, supplies travel
through the airport along with people.
This high volume of traffic, coupled with unusually dangerous winds,
brought Juneau International Airport to the attention of the FAA. The
area has two major airflows: a warm south to southeast wind from the Gulf
of Alaska and a north to northeast wind bringing cold air from the interior.
Under certain wind conditions, the only way to fly out of Juneau is by
making a slow, 180-degree turn just after takeoff while turbulent winds
coming over the mountains buffet the aircraft.
For several years, RAP has worked with the FAA, Alaska Airlines, the
Univeristy of North Dakota, the University of Oklahoma, and the University
of Wyoming to collect data in Juneau. In 1998, 2000, and 2002, RAP and
university staffers traveled to Juneau to collect wind data that have
been used to build and refine the warning system. This past winter, two
airplanes, the University of Wyomings King Air and a larger Alaska
Airlines Boeing 737-400, gathered data to fine-tune the prototype system.
The planes were used to correlate ground-system readings with actual
data from the planes. For further accuracy, the Doppler on Wheelsa
truckborne radar owned jointly by NCAR and the University of Oklahoma
that measures radial wind speedconfirmed the data.
With the cold winter weather and rough traveling conditions in Juneau,
Bob jokes that a lot of people have suffered on the project. But everyone
involved understands that the focus of the new system is safety. Turbulence
is a major concern for the airlines. In one serious incident in Juneau,
a 737 departing the airport fully loaded with passengers encountered a
wind hazard and rolled over more than 90 degrees. Fortunately in this
case, the pilots were able to get the airplane back upright just a few
hundred feet above the ground and complete their departure. The Juneau
warning system is designed to provide alerts that will allow pilots to
avoid these types of hazardous areas.
It will also help airlines save money. Turbulence costs U.S. airlines
an estimated $100 million each year in injuries and operational disruptions
such as delays and rerouting. In Juneau, high winds can last from 2 to
72 hours, and wind information can help airlines adjust their routes and
schedules to optimize usage of the airport.
The warning system features sophisticated technology. The wind
profilers have two computers, explains RAPs Deirdre Garvey.
One is part of the profiler and the other is a Debian Linux computer
running the RAP algorithms. The anemometers and wind profilers transmit
data to a central location at the airport, where final data analysis is
performed. There is also a wind information system in Juneau running a
set of RAP algorithms and sending the data to various remote locations
in Juneau. Despite all this technology, in the end, it is up to the pilot
to decide how to respond to the warnings.
RAP hopes to have the prototype completed and handed over to the FAA
by 2004. The FAA will then modify the system to fit its long-term needs.
In the meantime, RAP staffers will continue to refine the prototype alert
system and check it for accuracy.
Until the warning system is up and running, people will be sure to remember
to pull their seat belts tight on their next trip to Juneau. Bob sighs,
NCAR never seems to send me to a place where the weather is nice.
Before the Juneau project, RAP built a similar warning system at Hong
Kongs Chek Lap Kok Airport (above in an artists illustration),
which is scheduled to be completed as shown in 2040. Without this warning
system, called the Windshear and Turbulence Warning System (WTWS), research
showed that one in 700 flights would encounter severe wind shear and one
in 2,500 would encounter severe turbulence. With the WTWS system installed,
unexpected windshear and turbulence are rarely encountered. The WTWS is
equipped with a suite of wind shear and turbulence detection algorithms.
It processes data from anemometers and a terminal Doppler weather radar.
Also in this issue...
launching instrument collection
Lally wins prestigious ballooning award
special evening with an intimate of the atmosphere
PTO, health benefits, and diversity training
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