By Jason Paur
September 21, 2012
Hurricane researchers are gathering unprecedented data this month by using two NASA Global Hawk unmanned aircraft. The airplanes were originally developed for the military, but have been modified to aid in atmospheric research.
One of the Global Hawks was flown to its new base at NASA’s Wallops Island Flight Facility on Virginia’s Atlantic coast earlier this month and has already flown several missions over developing tropical storms giving atmospheric scientists the ability to watch and measure storms for up to three times as long as they could with manned aircraft, including NASA’s modified U-2 spyplane. The second Global Hawk is set to depart the Dryden Flight Research Center in California and join its hangar mate in the next week or so.
The airplanes were first used to observe storm development on a limited basis in 2010. The earlier missions were flown out of Dryden, which cut short the amount of time the planes could spend over Atlantic storms. Now based on the East Coast, the Global Hawks can spend up to six hours off the coast of Africa as storms develop, or 20 hours or more as the storms approach North America.
This long loiter capability is what has scientists excited to gain new insight into the life of a hurricane, says Scott Braun, principal investigator on NASA’s Hurricane and Severe Storm Sentinel (HS3) project.
“We’ve kind of gone from reconnaissance, which is short-term investigations” said Braun, “to more of surveillance where you can stay with a storm and move with it for a while.”
The path flown by Global Hawk AV-6 over tropical storm Nadine on Sept. 12. (NASA)
On Wednesday, the Global Hawk known as AV-6 departed Wallops Island and flew for nearly 25 hours observing tropical storm Nadine over the central Atlantic. It was the third time AV-6 had flown over the storm in the past 10 days. The airplane carries an “environmental payload” designed to gather big-picture data by flying around the entire storm (above). In addition to a high-resolution infrared sounder and cloud-physics LIDAR for measuring the structure and depth of clouds, AV-6 can make direct measurements by dropping out radiosondes that can measure temperature, humidity, wind speed and air pressure as they descend by parachute from as high as 60,000 feet.
The other airplane, AV-1 has a different suite of remote sensing instruments on board focused on the development of the inner core of the storms, measuring variables including wind profiles, rain rates and liquid water content of the clouds.
Researchers have learned a lot about predicting the path of hurricanes over the past several decades. But being able to predict the intensification of storms, especially early in their development has not been as successful. One of the aspects of storm and hurricane development Braun and the HS3 team are hoping to learn more about is the role dry, dusty air masses blowing off the Sahara play in the intensification process. It’s something debated in the research community, and until now scientists have had limited capabilities to watch the interaction for long periods of time.
“In some ways the Saharan air layer is essential,” Braun said. “The question is, once you develop these waves, to what extent can this dry and dusty air get into these disturbances to disrupt the ability of thunderstorms to get rotation organized on smaller scales to spin up a hurricane.”
Braun says most of the storms form from the air masses that come off Africa, but in manned aircraft they may only get a few hours at a time to watch and gather data. Satellites are also used extensively, but they offer a few snapshots a day and cannot make direct measurements. The Global Hawks provide the capability to watch the storms develop for up to a day at a time. And with two of them the researchers will eventually be able to watch storms continuously.
“We could potentially follow them all the way across the Atlantic, so you’re looking at the full life cycle of these storms.”
The Global Hawks will remain in Virginia through early October until hurricane season is over. The airplanes will be back on the East Coast for more long flights next year as well as in 2014.