Modeling The Paths Of Soaring Birds Helps Pilots

"Modern aircraft can sustain a two-pound bird strike on the windshield or in the engine with little difficulty," says Dr. George Young, associate professor of meteorology and geoenvironmental engineering. "However, multiple bird strikes can damage windshields and turbine engine blades." If a four-engine jet loses an engine it can still fly, but if a single engine plane loses an engine, it cannot. The U.S. military and commercial airlines would like to know where birds will be so that pilots can avoid bird impacts by adjusting their flight paths. However, until recently, this was not possible.

"Figuring this out required someone who knew something about birds, something about soaring and something about boundary layer meteorology," says Young who has done weather forecasting for glider competitions. The Center for Conservation Research and Technology (CCRT), a private/university/government partnership, in Baltimore, Md., asked Young to join their study.

Both soaring and flapping birds can cause problems, but the researchers began by investigating the soaring bird problem. Investigating American white pelicans, Saskatchewan Swainson's hawks and Texas turkey vultures, the researchers used ARGOS satellite system and tracking equipment to find the location and altitude of birds throughout the day. "Some days the birds soared two miles high and other days they went no more than 100 feet above the ground," says Young. "The American white pelican can go as high as 14,000 feet in just ten minutes on a good day, but will not go any higher." He notes that the cold or lack of oxygen may cause the 14,000-foot limit.

Once the researchers knew where the birds were, they realized that soaring birds soar using the same principles as gliders. Both gliders and soaring birds must rely on the warm rising columns of air called thermals created in the atmosphere's boundary layer. This layer is the portion of the atmosphere closest to the ground and affected by the ground. The height of the boundary layer changes depending on ground temperature. The typical soaring pattern follows the thermals, begins low in the morning and rises to a peak at noon. The height levels off and then drops in the evening after the sun sets.

"Meteorologists can forecast temperature highs and lows more accurately than they can forecast precipitation," says Young. "Luckily, it is the high and low temperatures that dictate how high the birds will soar."

Meteorologists have gotten very good at predicting how high thermals will go and can also predict high and low temperatures hours or days into the future. Harlan D. Shannon, a Penn State meteorology graduate student and CCRT member, Young, and Colin J. Pennycuick, University of Bristol, developed a model for bird flight forecasting. The model can tell pilots a day in advance how high the birds are likely to soar based on weather conditions so that they can plan flight routes and altitudes.

"We can ensure that pilots stay 500 to 1000 feet above the highest soaring bird each day and keep pilots, passengers and birds safe," says Young. "Now we need to study flapping birds and determine their migratory patterns and flight preferences."

The researchers have just begun to look at geese, swans and ducks that fly by flapping their wings rather than soaring.

"We can see these birds on weather radar," says Young. "In the next few years we hope we can make headway in determining where these flocks will be and where they will be going."