May 26, 2008

Exploring Hurricanes With Unmanned Drones

In an effort to learn more about giant storms, U.S. researchers are using unmanned, remote-controlled airplanes this year to penetrate the heart of Atlantic hurricanes.

However, for fear of endangering other planes, American aviation authorities have forced the rugged drones to be flown from the eastern Caribbean island of Barbados.

The drones look just like hobbyists' model airplanes but can be controlled by satellites. Storm researchers are confident the drones will give them a more complete picture of the core of cyclones than they've ever had before.

The drones can fly into the eye of a storm just 300 feet above the sea surface and send back a constant stream of temperature, pressure, wind and humidity readings.

"It can get measurements we couldn't get otherwise," said Joe Cione, a research meteorologist with the U.S. National Oceanic and Atmospheric Administration.

"That area of the storm is critical because that's where the maximum winds are. It will give us a better understanding of where the energy is extracted out of the sea."

The 7-feet long aircraft are made by Australia's Aerosonde Pty Ltd. and are worth between $50,000 and $80,000. They boast a 9-foot wingspan and weigh only 28 pounds.

Powered by a tiny 24 cc motor and a single propeller, they can fly at about 70 mph (113 kph) and cover an astonishing 2,000 miles on a single 0.66 U.S. gallon (2.5-litre) tank of fuel, Cione said. They are much smaller and less sophisticated than those used by the U.S. military in war zones.

The drones can be catapulted into flight or launched from a moving vehicle. They are initially flown by a joystick before control is transferred to a laptop and then to satellite.

Unlike the manned hurricane hunter aircraft used for years to penetrate cyclones at around 10,000 feet, the Aerosondes will fly a few hundred feet above the ocean, where the critical energy transfer from sea surface to storm occurs.

For years scientists have taken measurements using "dropsondes," packages of instruments flung from a plane that take "snapshots" as they fall through the storm. The new drones offer a continuous data stream that will be a huge improvement over the sporadic measurements taken from dropsondes.

"It's the difference between taking a photograph and taking a movie," Cione said. "You're not going to miss anything."

Researchers first tested drones in 2005 during Tropical Storm Ophelia. Last year, an unmanned aircraft spent 17.5 hours aloft in a flight into Hurricane Noel.

Researchers are hoping for at least two to five flights this year.

For this hurricane season"”which starts Saturday and runs for six months"”the drones will be forced to fly far from U.S. shores. The Federal Aviation Administration has not given NOAA approval to fly them from U.S. territory.

The agency has issued more than 100 approvals for unmanned aircraft on projects ranging from searches for illegal aliens along the U.S. border to wildfire surveillance.

The FAA said it must be sure the drones could be flown safely from a U.S. base into an approaching hurricane, a time when many pilots are moving small planes out of harm's way.

"You have a situation where you have a small aircraft that has no real ability to see and avoid other aircraft, transiting an area that might have civilian aircraft in it," FAA spokesman Les Dorr said.

Researchers in the U.S. hope for eventual approval for flights within the country in order to give them a chance to study hurricanes nearing the coast for signs of the explosive intensity surges scientists find most worrisome.

"Once that option's available to us, we'll be all over it," Cione said. "That's in the FAA's camp."

For weather forecasters, predicting sudden, rapid intensification is one of their weaknesses. A relatively mild hurricane approaching a crowded shore can become a destructive cyclone with winds over 130 mph (210 kph) after residents have gone to bed, leaving little time to evacuate once they awaken.

The drones may capture a better picture of the inner core, the eye wall and especially the energy exchange at the sea surface that fuels hurricanes"”offering a better chance to improve intensity forecasting.

"Personally, my feeling is that we can make leaps and bounds -- big, pioneering changes in our understanding of intensity," Cione said.


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