Intercomparison of Remotely Sensed Atmospheric Profiles with Dropsonde Observations from the Global Hawk Unmanned Aircraft

The NASA Global Hawk unmanned aircraft has been used in several NOAA/NASA missions over the last four years, including SHOUT (Sensing Hazards using Operational Unmanned Technology), HS3 (Hurricane and Severe Storm Sentinel) and WISPAR (Winter Storms and Pacific Atmospheric Rivers). Two instruments in particular, HAMSR (High-Altitude MMIC Sounding Radiometer) and Scanning-HIS (High-resolution Interferometer Sounder) are remote sensors installed on the aircraft capable of providing cross-track swaths of upper air, surface, and vertical profile information using derivations from brightness temperature measurements. In this study, both instruments are simultaneously compared alongside AMSR-E satellite and dropsonde data from AVAPS (Airborne Vertical Atmospheric Profiling System) to assess their ability to give accurate, detailed meteorological state information as well as fill potential satellite gaps. Of particular interest is the integrity of the column liquid water content measurements crucial to hurricane and atmospheric river forecasting and modeling. In 2011, an HS3 test flight was flown with the Global Hawk over a large stretch of the Pacific Ocean with all three mobile instruments on board. This study provides a detailed comparison of the accuracy and dependability of the moisture measurements throughout that flight. S-HIS data from the 2014 Hurricane Edouard mission is also compared with coincident dropsonde data to provide a more realistic extreme weather context to assess probable performance on future flights and the impact of improved retrieval algorithms on data quality. Both HAMSR and S-HIS returned favorable results despite some anomalies in extreme dry or cold conditions, or with high-level clouds present.