There’s only so much that we can learn about hurricanes by looking at them from the ground, or by observing them using distant satellites. Aircraft, on the other hand, give researchers an aerial view of the weather systems, while also allowing for direct measurements of variables such as temperature and humidity – the one catch is, would you want to be in a plane that was circling over a hurricane? Probably not. That’s one of the reasons why NASA is using Global Hawk UAVs (unmanned aerial vehicles) to study hurricanes off the east coast of the U.S.

The agency’s month-long Hurricane and Severe Storm Sentinel (HS3) mission, which started last week and lasts into early October, will incorporate two Global Hawks. The first one has already flown from its home base at Edwards Air Force Base, California to its mission base at NASA’s Wallops Flight Facility on Wallops Island, Virginia, landing there last Friday. On the way, however, it spent ten hours over the Atlantic Ocean, gathering data on Hurricane Leslie.

That first UAV is equipped with three instruments, for the sampling the environment surrounding hurricanes. These instruments include the laser-based Cloud Physics Lidar (CPL) system, which measures cloud structure and aerosols such as dust, sea salt and smoke particles; the Scanning High-resolution Interferometer Sounder (S-HIS), which remotely measures the temperature and water vapor vertical profile, plus the sea surface temperature; and the Advanced Vertical Atmospheric Profiling System (AVAPS), which measures winds, temperature and humidity by dropping small parachute-equipped sensors into the storm.

The flight path taken by the first of the UAVs, last Thursday/Friday (Image: NASA)

The second aircraft, which is due to arrive in two weeks, will have a different set of instruments, designed for studying the interiors of hurricanes and developing storms. These will include Doppler radar, along with microwave sensors such as the High-altitude Imaging Wind and Rain Airborne Profiler (HIWRAP), which allows for a 3D view of cloud structure and wind conditions; the High-Altitude MMIC Sounding Radiometer (HAMSR), which utilizes microwave wavelengths to measure temperature, water vapor, and precipitation from the top level of the hurricane to the surface of the ocean; and the Hurricane Imaging Radiometer (HIRAD), which is used to measure rain rates and wind speeds.

Both Global Hawks are remotely controlled by ground-based pilots, can reach altitudes of over 60,000 feet (18,288 meters), and are capable of staying aloft for up to 28 hours.

“The mission targets the processes that underlie hurricane formation and intensity change,” NASA stated in a press release. “The aircraft help scientists decipher the relative roles of the large-scale environment and internal storm processes that shape these systems.”

Following its study of Hurricane Leslie last week, the first UAV proceeded to observe the “birth” of Tropical Storm Nadine this Tuesday and Wednesday.

Source: NASA