_:genid1 ""^^ . _:genid2 . _:genid3 . _:genid3 "Satellite microwave sensors are used to determine the predominant frozen or thawed status of water on the land surface at a given time. Spatial measurements are taken over the contiguous United States and Alaska and include all vegetated land areas where seasonal frozen temperatures are a major constraint to growth. Non-frozen season data are converted to degrees F and aggregated. Anomalies are shown relative to the 1979-2010 average. \r\n\r\nThe data used are from January 1, 1979 to December 31, 2010.\r\n\r\nData was accessed on September 17, 2014."^^ . _:genid4 . _:genid4 _:genid2 . _:genid4 _:genid3 . "134d344e-indicator-frost-free-season-process" . _:genid1 . _:genid4 . . . .