On the Dependence of Satellite Soundings on Instrument Field-of-View Size — A Study to Support Improvements in the CrIS Sensor Design

This presentation provides the results of a study conducted with high spatial resolution (1-2 km) hyperspectral sounding retrievals obtained with the UW S-HIS instrument flying onboard the high altitude (15 -20 km) Global Hawk (GH) unmanned NASA aircraft.  In addition to the S-HIS, the GH carried a high-density dropsonde system, useful for validating the S-HIS profile retrievals, as well as a Cloud Physics Lidar (CPL), useful for validating the cloud top altitude impacting the S-HIS sounding retrievals. The GH, with the S-HIS onboard, participated in three Hurricane and Severe Storm Sentinel (HS3) observation missions over the tropical Atlantic during the hurricane seasons of 2012, 2013, 2014.  CrIS retrievals for various assumed FOV sizes are obtained by spatially averaging the single sample full spatial resolution S-HIS retrievals to the assumed FOV size of a future CrIS instrument.    If any of the S-HIS retrievals used to obtain the CrIS FOV average retrieval is cloudy, then the CrIS FOV average sounding is presumed to be missing below the S-HIS determined cloud level.  The accuracy of the retrievals for various FOV sizes is determined through direct comparisons of the retrievals with simultaneous dropsonde measurements. Both the sounding yield (i.e., the number of CrIS soundings obtained for a given FOR size (e.g., 50-km) and the accuracy, based on the dropsonde comparisons, are determined for each of the potential CrIS FOV sizes.  Various detector array configurations are considered, ranging from the current 3 x 3 detector array size to an array size that provides contiguous sampling within the current 50-km, in linear dimension, Field-of-Regard (FOR).   Smaller FOR sizes are also considered in order to demonstrate the impact of FOV size on the production of higher spatial resolution retrievals for mesoscale storm prediction applications.