SAN FRANCISCO — In August, NASA plans to begin flying two Global Hawk unmanned aircraft in an intensive campaign to gain insight into the dynamics of hurricane intensity change in the Atlantic Ocean basin.
“We are pretty good about predicting the track of a hurricane,” said Marilyn Vasques, program manager for the Hurricane and Severe Storm Sentinel (HS3) at the NASA Ames Research Center in Moffett Field, Calif. Meteorologists are less adept, however, at determining whether a storm is likely to intensify.
“The most difficult thing we face as forecasters is understanding whether a storm will change from a Category 1 storm to a Category 3 storm suddenly, slowly or not at all,” said Jeffrey Halverson, a co-investigator on the HS3 science team and geography professor at the University of Maryland, Baltimore County.
For the HS3 mission, scheduled to begin Aug. 20 and run through Sept. 23, NASA plans to fly two Global Hawks equipped with instruments to measure atmospheric humidity, pressure, temperature, aerosols and wind speed, Vasques said.
One aircraft features instruments designed to gather data while peering down through clouds and precipitation at the “guts of the storm,” said Bernadette Luna, HS3 deputy project manager at NASA Ames. That instrument suite, dubbed the Over-Storm Payload, features: a conically scanning Doppler radar, known as High-Altitude Imaging Wind and Rain Airborne Profiler; a multifrequency interferometric radiometer, called Hurricane Imaging Radiometer; and the High Altitude Monolithic Microwave integrated Circuit Sounding Radiometer.
The second HS3 aircraft is equipped with sensors to observe atmospheric conditions in the immediate vicinity of the storm. The Environmental Payload on that aircraft features: the High-resolution Interferometer Sounder to provide data on atmospheric temperature and water vapor; an airborne Doppler lidar, called Tropospheric Wind Lidar Technology Experiment; the Cloud Physics Lidar; and dropsondes, devices created by the National Center for Atmospheric Research to measure storm conditions as they fall from aircraft to the ground.
It was those dropsondes that provided an early indication of the utility of the HS3 program. In 2012, the initial year of the five-year HS3 mission, NASA dropped 300 dropsondes into Tropical Storm Nadine during five Global Hawk flights. Data drawn from the dropsondes showed forecasters that Nadine, which eventually strengthened into a hurricane, was not weakening as quickly as they expected, Vasques said.
Data gathered during the 2013 HS3 mission will be fed directly into forecasting models to help meteorologists track the birth of hurricanes, their intensification, decay and transition to mid-latitude storm systems, Halverson said.
Those observations also will be used to improve computer models. Once scientists obtain a more thorough understanding of the physical processes that cause hurricanes to intensify, they can use that information to refine the existing models forecasters rely on to predict the course of storms, Halverson said.
Additional observations of hurricane conditions will come from piloted aircraft. NASA project managers are coordinating the upcoming HS3 campaign with National Oceanic and Atmospheric Administration (NOAA) and U.S. Air Force officials planning research flights for NOAA’s P-3 Orion turboprop, NOAA’s Gulfstream 4 jet and the Air Force C-130 Hurricane Hunter.
During the 2012 hurricane season, NASA conducted the HS3 mission with a single Global Hawk based at NASA’s Dryden Flight Research Center in Edwards, Calif. This year, NASA plans to fly two Global Hawks from NASA’s Wallops Flight Facility in Virginia, “a very good base to observe storms approaching the Eastern seaboard,” Halverson said.
Aided by the long-duration Global Hawk, HS3 researchers are seeking to obtain unprecedented multiday coverage of storm cycles. Each aircraft is designed to fly at altitudes of 17,000 meters and fly for as long as 26 hours.
While the two aircraft will not fly simultaneously, the second Global Hawk is expected to take off within three hours of the first aircraft’s landing. Through interagency coordination, even that brief gap could be eliminated. “It would be great if the NOAA P-3 was flying in the same storm during that three hour gap,” Vasques said.
Data gathered during the Global Hawk flights also will be used in conjunction with satellite observations to provide a more thorough picture of hurricanes. Satellites, including NOAA’s Geostationary Operational Environmental Satellites and the joint NASA-Japan Aerospace Exploration Agency Tropical Rainfall Measurement Mission, offer a wealth of data on storm conditions worldwide, but do not offer the detailed measurement of individual storms provided by the long-duration Global Hawk, Halverson said.
NASA’s Earth Science Division is sponsoring the HS3 mission as part of its Earth Ventures program of competitively selected, science campaigns.