期刊
REMOTE SENSING OF ENVIRONMENT
卷 194, 期 -, 页码 48-62出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.rse.2017.03.007
关键词
SMAP; Radar; Passive microwave; Freeze/thaw
资金
- National Aeronautics and Space Administration
- National Science Foundation [PLR-1304464]
- National Science Foundation Division of Polar Programs Arctic Observatory Network [0632264, 1107892]
- Canadian Space Agency
- Office of Polar Programs (OPP)
- Directorate For Geosciences [1107892, 1503912, 1545558, 1623764] Funding Source: National Science Foundation
- Office of Polar Programs (OPP)
- Directorate For Geosciences [0632264, 1304464] Funding Source: National Science Foundation
Over one-third of the global land area undergoes a seasonal transition between predominantly frozen and non-frozen conditions each year, with the land surface freeze/thaw (FT) state a significant control on hydrological and biospheric processes over northern land areas and at high elevations. The NASA Soil Moisture Active Passive (SMAP) mission produced a daily landscape FT product at 3-km spatial resolution derived from ascending and descending orbits of SMAP high-resolution L-band (1.4 GHz) radar measurements. Following the failure of the SMAP radar in July 2015, coarser (36-km) footprint SMAP radiometer inputs were used to develop an alternative daily passive microwave freeze/thaw product. In this study, in situ observations are used to examine differences in the sensitivity of the 3-km radar versus the 36-km radiometer measurements to the landscape freeze/thaw state during the period of overlapping instrument operation. Assessment of the retrievals at high-latitude SMAP core validation sites showed excellent agreement with in situ flags, exceeding the 80% SMAP mission accuracy requirement. Similar performance was found for the radar and radiometer products using both air temperature and soil temperature derived FT reference flags. There was a tendency for SMAP thaw retrievals to lead the surface flags due to the influence of wet snow cover conditions on both the radar and radiometer signal. Comparison with other satellite derived FT products showed those derived from passive measurements (SMAP radiometer; Aquarius radiometer; Advanced Microwave Scanning Radiometer - 2) retrieved less frozen area than the active products (SMAP radar; Aquarius radar). Crown Copyright (C) 2017 Published by Elsevier Inc.
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