The primary objective of the NOAA-led Winter Storms and Pacific Atmospheric Rivers (WISPAR) campaign was to demonstrate the operational and research applications of the dropsonde system, developed for NOAA by the National Center for Atmospheric Research (NCAR) for use on the NASA Global Hawk (GH) unmanned aircraft. The GH flew three research flights for a total of almost 70 hours in February–March 2011 deploying a total of 177 dropsondes from near 60,000 feet altitude into atmospheric rivers (ARs), winter storms, and the remote Arctic atmosphere. The AVAPS (Airborne Vertical Atmospheric Profiling System) dropsonde measurements provide high-resolution in situ thermodynamic and wind data between the lower stratosphere and the surface of the ocean. In addition, the NASA Jet Propulsion Laboratory operated HAMSR, a microwave-based remote sensing instrument, on the GH during WISPAR. Observed HAMSR radiances are used to retrieve vertically resolved temperature and water vapor data between the aircraft and the surface. HAMSR provides areal coverage in a swath 65 km wide at the surface with 1–2 km vertical resolution and can be used to provide continuity between the dropsonde measurements, and given its similarity to satellite sensors, can be used to provide a link between the dropsonde and satellite observations. Together, the data acquired from these instruments can be used to improve the understanding of the structure and evolution of ARs and winter storms.

On the first science flight, the GH released 37 sondes in a well-developed AR near its source of deep moisture in the tropics north and east of Hawaii. ARs are narrow regions of enhanced water vapor transport that often emerge from the tropics and can lead to major rain and flooding events upon landfall. The observations from this flight provide important new information on how water vapor is transported from the tropics to midlatitudes in ARs. The second flight explored the potential of the GH to collect targeted observations coordinated with the Winter Storms Reconnaissance Program. The GH deployed 70 sondes into a developing winter storm in the North Pacific with the goal of improving successive model forecasts of the storm's impact on the southeast US a few days later. The GH flight was coordinated with an operational flight of the NOAA G-IV aircraft to address the winter storms objectives. On the third flight, the GH flew an unprecedented mission into the Arctic stratospheric vortex in March reaching as far north as 85 degrees latitude. Thirty-five sondes were released in the Arctic and another 35 were deployed in an AR and winter storm off the west coast of North America during the 25 hour flight. The dropsonde deployments in the Arctic demonstrate the capability of the GH to conduct operations in remote regions of the earth's atmosphere and the value of observations in the Arctic atmosphere where in situ measurements are very limited.