NASA mission analyzes Saharan dust layer over eastern Atlantic

NASA: One of two of NASA's Global Hawk unmanned aircraft flew over the remnants of Tropical Storm Erin and investigated the Saharan Air Layer in the Eastern Atlantic Ocean on Aug. 20 and 21. The instruments aboard the Global Hawk sampled the environment of ex-Erin and revealed an elevated dust layer overrunning the storm.

"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," said Scott A. Braun, HS3 principal investigator and a research meteorologist at NASA's Goddard Space Flight Center in Greenbelt, Md.

Two Global Hawks are flying as part of HS3, short for NASA's Hurricane and Severe Storm Sentinel mission, this year out of NASA’s Wallops Flight Facility at Wallops Island, Va. Global Hawk aircraft are well-suited for hurricane investigations because they can fly for as long as 28 hours and over-fly hurricanes at altitudes greater than 60,000 feet (18.3 km).

One of the purposes of the HS3 mission is to address the controversial role of the Saharan Air Layer in tropical storm formation and intensification. On its first flight out of Wallops, a Global Hawk obtained data about the SAL using several instruments aboard.

The Cloud Physics Lidar, or CPL, instrument analyzed the SAL and showed an elevated dust layer between about 1.5 and 2.8 miles (2.5 and 4.5 km) overrunning the remnants of Erin. The low-level clouds associated with what was left of Erin were located below 1.2 miles (2 km). The CPL is an airborne lidar system designed specifically for studying clouds and aerosols. CPL will study cloud- and dust-layer boundaries and will provide optical depth or thickness of aerosols and clouds....

This infrared image from NOAA's GOES-East satellite on Aug. 20 shows the Global Hawk crossing the low-level remnants of Erin. Erin's low-level clouds appear as a faint circulation. The green path is the direction the Global Hawk came from. The red line represents the path the aircraft would follow.
Image Credit: NASA/NOAA