The NASA Global Hawk completed a field campaign March 10. (NASA Photo / Carla Thomas)
› View Larger Image A NASA Global Hawk aircraft completed the third and final flight of the Winter Storms and Pacific Atmospheric Rivers, or WISPAR, field campaign March 10, 2011. The long-duration flights over the Pacific Ocean explored atmospheric rivers and Arctic weather and collected targeted observations designed to improve operational weather forecasts.
The National Oceanic and Atmospheric Administration-led WISPAR airborne campaign that began Feb. 11 was focused on improving scientists' understanding of how atmospheric rivers form and behave and evaluating the operational use of unmanned, high-altitude aircraft for investigating these phenomena. The research is also designed to assist NOAA in conducting potential offshore monitoring of atmospheric rivers to aid in future weather predictions.
Atmospheric rivers are narrow regions in Earth's atmosphere that transport large amounts of water vapor across the Pacific Ocean or other regions. Aptly nicknamed "rivers in the sky," they can transport enough water vapor in one day, on average, to flood an area the size of Maryland one foot deep, an amount that constitutes nearly seven times the average daily flow of water from the Mississippi River to the Gulf of Mexico.
An automated dropsonde system, developed for NOAA by the National Center for Atmospheric Research, was installed on NASA's Global Hawk for the study. When dispensed from the aircraft, a sonde - about the size of a paper towel roll - collects readings on temperature, wind, relative humidity and other elements as it descends through an atmospheric river or other weather feature.
"The experiment was very successful in evaluating the combined capabilities of the dropsonde system on the Global Hawk and exploring potential scientific and operational applications for NOAA," said Gary Wick, a physicist in the Physical Sciences Division of the NOAA Earth System Research Laboratory, Boulder, Colo. "I was very impressed with the ability and willingness of the NASA team to modify the flight plans and scheduled drop locations in real time."
Also aboard the Global Hawk was the High-Altitude Monolithic Microwave Integrated Circuit Sounding Radiometer, or HAMSR, an advanced water vapor sensor. Developed by NASA's Jet Propulsion Laboratory in Pasadena, Calif., HAMSR analyzes heat radiation emitted by oxygen and water molecules in the atmosphere to determine their density and temperature.
The HAMSR operates at microwave frequencies that can penetrate clouds, enabling the instrument to determine temperature, humidity and cloud structure under all weather conditions. This capability is critical for studying atmospheric processes associated with bad weather, such as the conditions present in atmospheric river events.
"HAMSR worked flawlessly during the WISPAR campaign and was essentially operating autonomously, with no intervention required during the flights," said HAMSR principal investigator Bjorn Lambrigtsen. "The real-time data-display capability provided situational awareness and was used to assist in executing the flights, as was also done previously in the GRIP hurricane mission. The HAMSR data will be used by NOAA and JPL scientists to investigate the atmospheric river phenomenon."
The unmanned Global Hawk took off from Dryden Feb. 11 on the first atmospheric rivers flight, landing 20 hours later. During the flight, made to investigate atmospheric rivers in the Pacific, 37 dropsondes were dispensed, the first use of a dropsonde system on the aircraft. During the three flights a total of 177 dropsondes were dispensed.