Thursday, October 14, 2010

NASA Loosens GRIP On Atlantic Hurricane Season

Atlantic Hurricane Season
NASA wrapped up one of its largest hurricane research efforts ever last week after nearly two months of flights that broke new ground in the study of tropical cyclones and delivered data that scientists will now be able to analyze for years to come.

While the 2010 hurricane season has been a rather quiet one for coastal dwellers, the churning meteorology of the Atlantic Ocean and Caribbean Sea seemed to cooperate well with the science goals of Genesis and Rapid Intensification Processes (GRIP) experiment. Those goals were designed to answer some of the most fundamental yet still unanswered questions of hurricane science: What ultimately causes hurricanes to form? Why do some tropical depressions become strong hurricanes, while others dissipate? What causes the rapid strengthening often seen in hurricanes?

Mission scientists wanted to capture data on hurricanes as they formed and intensified. Ideally, the NASA planes – the DC-8, WB-57 and Global Hawk – would also fly over systems that were weakening, or that were expected to form into hurricanes yet did not. When the flights had ended, all those goals had been met.

“It was successful beyond my reasonable expectations. It requires cooperation with the weather, and good luck with the aircraft,” said mission scientist Ed Zipser, of the University of Utah. “It's not so much a logistical challenge as it is a toss of the dice by Mother Nature during our time available. But it takes a good airplane, a skillful crew and good luck with the equipment.”

Flying to Hurricanes

Hurricanes Earl and Karl each became important objects of observation for scientists during GRIP. The DC-8 flew to Earl four times, criss-crossing the storm as it intensified to a category 4 hurricane and then weakened. On the final Earl flight, as the storm was breaking down and losing strength, the Global Hawk made its debut hurricane flight and passed over Earl’s eye in concert with the DC-8, providing valuable comparison measurements for the instruments on-board both aircraft. The WB-57 also flew Earl as well as Karl.

At the outset, scientists hoped that several aspects of GRIP would help gather important data as well as complete a couple of technical accomplishments. First, collaboration with the Air Force, NOAA and the National Science Foundation would allow scientists to observe a single storm system with as many as six aircraft. Second, GRIP featured the debut of NASA’s Global Hawk drone in a hurricane research capacity. The unmanned plane’s 24-hour flight range gave scientists the ability to directly observe a hurricane as it changed over time and distance in a way that conventional planes and satellites have not done before.

Both of these aspects of GRIP were used to great effect during the two major hurricanes observed during the campaign, Earl and Karl. “We’re all very pleased we were able to get the Global Hawk over a hurricane,” said mission scientist Gerry Heymsfield, of NASA’s Goddard Space Flight Center, Greenbelt, Md. “There was a question about that. That’s a major accomplishment both on the science side and the capability side. It really paves the way for future research.”

As the campaign went on, Global Hawk pilots, based remotely at Dryden Flight Research Center, near Palmdale, Calif., grew more comfortable with the drone’s capability at 60,000 feet and over a hurricane. On Sept. 16 and 17, the Global Hawk made a 25-hour flight that included 20 passes over the eye of Karl as it was emerging into a hurricane – precisely the type of formation and storm development that scientists hoped to capture during GRIP.


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