{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,31]],"date-time":"2026-03-31T09:54:35Z","timestamp":1774950875037,"version":"3.50.1"},"reference-count":41,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2018,9,17]],"date-time":"2018-09-17T00:00:00Z","timestamp":1537142400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"NASA Research Opportunities in Earth and Space Sciences (ROSES)","award":["NNX16AN34G"],"award-info":[{"award-number":["NNX16AN34G"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Seasonal freeze-thaw (FT) impacts much of the northern hemisphere and is an important control on its water, energy, and carbon cycle. Although FT in natural environments extends south of 45\u00b0N, FT studies using the L-band have so far been restricted to boreal or greater latitudes. This study addresses this gap by applying a seasonal threshold algorithm to Soil Moisture Active Passive (SMAP) data (L3_SM_P) to obtain a FT product south of 45\u00b0N (\u2018SMAP FT\u2019), which is then evaluated at SMAP core validation sites (CVS) located in the contiguous United States (CONUS). SMAP landscape FT retrievals are usually in good agreement with 0\u20135 cm soil temperature at SMAP grids containing CVS stations (&gt;70%). The accuracy could be further improved by taking into account specific overpass time (PM), the grid-specific seasonal scaling factor, the data aggregation method, and the sampling error. Annual SMAP FT extent maps compared to modeled soil temperatures derived from the Goddard Earth Observing System Model Version 5 (GEOS-5) show that seasonal FT in CONUS extends to latitudes of about 35\u201340\u00b0N, and that FT varies substantially in space and by year. In general, spatial and temporal trends between SMAP and modeled FT were similar.<\/jats:p>","DOI":"10.3390\/rs10091483","type":"journal-article","created":{"date-parts":[[2018,9,17]],"date-time":"2018-09-17T10:42:20Z","timestamp":1537180940000},"page":"1483","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":24,"title":["Evaluation of SMAP Freeze\/Thaw Retrieval Accuracy at Core Validation Sites in the Contiguous United States"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7955-920X","authenticated-orcid":false,"given":"Simon","family":"Kraatz","sequence":"first","affiliation":[{"name":"Department of Civil and Environmental Engineering, University of New Hampshire, Durham, NH 03824, USA"}]},{"given":"Jennifer M.","family":"Jacobs","sequence":"additional","affiliation":[{"name":"Department of Civil and Environmental Engineering, University of New Hampshire, Durham, NH 03824, USA"}]},{"given":"Ronny","family":"Schr\u00f6der","sequence":"additional","affiliation":[{"name":"Department of Civil and Environmental Engineering, University of New Hampshire, Durham, NH 03824, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1841-6939","authenticated-orcid":false,"given":"Eunsang","family":"Cho","sequence":"additional","affiliation":[{"name":"Department of Civil and Environmental Engineering, University of New Hampshire, Durham, NH 03824, USA"}]},{"given":"Michael","family":"Cosh","sequence":"additional","affiliation":[{"name":"USDA ARS Hydrology and Remote Sensing Laboratory, Beltsville, MD 20705, USA"}]},{"given":"Mark","family":"Seyfried","sequence":"additional","affiliation":[{"name":"USDA ARS Northwest Watershed Research Center, Boise, ID 83712, USA"}]},{"given":"John","family":"Prueger","sequence":"additional","affiliation":[{"name":"USDA ARS National Laboratory for Agriculture and the Environment, Ames, IA 50011, USA"}]},{"given":"Stan","family":"Livingston","sequence":"additional","affiliation":[{"name":"USDA ARS National Soil Erosion Research Laboratory, West Lafayette, IN 47907, USA"}]}],"member":"1968","published-online":{"date-parts":[[2018,9,17]]},"reference":[{"key":"ref_1","first-page":"8860","article-title":"Investigation of the near-surface soil freeze-thaw cycle in the contiguous United States: Algorithm development and validation","volume":"108","author":"Zhang","year":"2003","journal-title":"J. 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