Global Hawk Aircraft Takes A Look At Saharan Air Layer And Tropical Storm Erin Remnants
August 24, 2013

NASA Hurricane Mission Studying Remnants Of Tropical Storm Erin

redOrbit Staff & Wire Reports - Your Universe Online

One of NASA’s two Global Hawk unmanned aircraft recently investigated the Saharan Air Layer (SAL) in the Eastern Atlantic Ocean as part of the ongoing Hurricane and Severe Storm Sentinel (H3) mission, officials from the US space agency revealed on Friday.

In addition to studying this intensely dry, warm and sometimes dust-laden layer of the atmosphere which often overlies the cooler, more-humid surface air of the Atlantic Ocean, the vehicles also viewed the remnants of Tropical Storm Erin as part of flights that occurred on August 20 and 21.

During those excursions, the instruments aboard the Global Hawk sampled the environment of Erin’s remains, while also revealing an elevated dust layer overrunning the storm, NASA said.

“Our goal with this flight was to look at how the Saharan air would move around or into the former storm, but the circulation was so shallow and weak that, according to our instruments, the Saharan air simply moved westward right over what was left of Erin,” explained Dr. Scott A. Braun, the HS3 principal investigator and a research meteorologist at NASA's Goddard Space Flight Center.

As part of the HS3 mission, two Global Hawks are currently flying out of the NASA Wallops Flight Facility at Wallops Island, Virginia. These aircraft are reportedly well-suited for hurricane investigation, because they are capable of flying for up to 28 hours at a time and can fly over storms at altitudes of more than 60,000 feet.

HS3 is a five-year mission designed to enhance our understanding of the processes that underlie hurricane intensity change in the Atlantic Ocean basin. It will also determine the extent to which either the environment or processes internal to the storm are essential to intensity change, and one of the purposes of the mission is to address the role that the SAL plays in tropical storm formation and intensification.

The Global Hawk used several instruments to obtain data about the SAL. Among them was the Cloud Physics Lidar (CAL), which analyzed the atmospheric region and showed an elevated dust layer between about 1.5 and 2.8 miles overrunning the remnants of Erin.

This airborne lidar system, designed specifically to study clouds and aerosols, also revealed that the low-level clouds associated with the remnants of Erin were located below 1.2 miles. According to NASA, CPL will study cloud- and dust-layer boundaries and will provide optical depth or thickness of aerosols and clouds.

A second instrument carried aboard the Global Hawk, the scanning High-resolution Interferometer Sounder, was used to measure temperature and dewpoint and discovered very dry air located above the remnants of Erin, Braun said. The Global Hawk is expected to return to the SAL for additional analysis this weekend.

The HS3 mission is scheduled to operate through September 30, and in addition to Wallops, several other NASA facilities (including the Earth Science Project Office at the Ames Research Center, which manages the project) are involved in the research. The mission is funded by NASA Headquarters in Washington.