Mapping Freezing and Thawing Surface State Periods With the CYGNSS Based F/T Seasonal Threshold Algorithm

Freeze/Thaw (F/T) surface state detection and imaging has been demonstrated as a capability of NASA's Cyclone Global Navigation Satellite System mission. The objective of the research presented here is the application of an existing F/T retrieval algorithm to multiple target areas over several years in order to demonstrate the ability to provide long term trending of F/T behavior. Metrics are developed and evaluated to characterize F/T trends related to global warming. They include the annual fraction of time spent frozen and thawed as a function of location and year, and the earliest fall freeze and earliest spring thaw as a function of location and year. The results demonstrate the capability of Global Navigation Satellite Systems Reflectometry to provide long term trending of F/T behavior relevant to studies of climate change.