Development and assessment of the SMAP enhanced passive soil moisture product

Publication: Research - peer-reviewJournal article – Annual report year: 2018

Without internal affiliation

DOI

  • Author: Chan, S. K.

    Jet Propulsion Laboratory, California Institute of Technology

  • Author: Bindlish, R.

    NASA Goddard Space Flight Center

  • Author: O'Neill, P.

    NASA Goddard Space Flight Center

  • Author: Jackson, T.

    U.S. Department of Agriculture

  • Author: Njoku, E.

    Jet Propulsion Laboratory, California Institute of Technology

  • Author: Dunbar, S.

    Jet Propulsion Laboratory, California Institute of Technology

  • Author: Chaubell, J.

    Jet Propulsion Laboratory, California Institute of Technology

  • Author: Piepmeier, J.

    NASA Goddard Space Flight Center

  • Author: Yueh, S.

    Jet Propulsion Laboratory, California Institute of Technology

  • Author: Entekhabi, D.

    Massachusetts Institute of Technology

  • Author: Colliander, A.

    Jet Propulsion Laboratory, California Institute of Technology

  • Author: Chen, F.

    Science Systems and Applications, Inc.

  • Author: Cosh, M. H.

    U.S. Department of Agriculture

  • Author: Caldwell, T.

    University of Texas at Austin

  • Author: Walker, J.

    Monash University

  • Author: Berg, A.

    University of Guelph

  • Author: McNairn, H.

    AgriFood Canada

  • Author: Thibeault, M.

    Comisión Nacional de Actividades Espaciales (CONAE)

  • Author: Martínez-Fernández, J.

    Universidad de Salamanca

  • Author: Uldall, F.

    Technical University of Denmark

  • Author: Seyfried, M.

    U.S. Department of Agriculture

  • Author: Bosch, D.

    U.S. Department of Agriculture

  • Author: Starks, P.

    U.S. Department of Agriculture

  • Author: Holifield Collins, C.

    U.S. Department of Agriculture

  • Author: Prueger, J.

    U.S. Department of Agriculture

  • Author: van der Velde, R.

    University of Twente

  • Author: Asanuma, J.

    University of Tsukuba

  • Author: Palecki, M.

    NOAA

  • Author: Small, E. E.

    University of Colorado Boulder

  • Author: Zreda, M.

    University of Arizona

  • Author: Calvet, J.

    CNRM Centre National de Recherches Meteorologiques

  • Author: Crow, W. T.

    U.S. Department of Agriculture

  • Author: Kerr, Y.

    CESBIO-CNES

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Launched in January 2015, the National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) observatory was designed to provide frequent global mapping of high-resolution soil moisture and freeze-thaw state every two to three days using a radar and a radiometer operating at L-band frequencies. Despite a hardware mishap that rendered the radar inoperable shortly after launch, the radiometer continues to operate nominally, returning more than two years of science data that have helped to improve existing hydrological applications and foster new ones. Beginning in late 2016 the SMAP project launched a suite of new data products with the objective of recovering some high-resolution observation capability loss resulting from the radar malfunction. Among these new data products are the SMAP Enhanced Passive Soil Moisture Product that was released in December 2016, followed by the SMAP/Sentinel-1 Active-Passive Soil Moisture Product in April 2017. This article covers the development and assessment of the SMAP Level 2 Enhanced Passive Soil Moisture Product (L2_SM_P_E). The product distinguishes itself from the current SMAP Level 2 Passive Soil Moisture Product (L2_SM_P) in that the soil moisture retrieval is posted on a 9 km grid instead of a 36 km grid. This is made possible by first applying the Backus-Gilbert optimal interpolation technique to the antenna temperature (TA) data in the original SMAP Level 1B Brightness Temperature Product to take advantage of the overlapped radiometer footprints on orbit. The resulting interpolated TA data then go through various correction/calibration procedures to become the SMAP Level 1C Enhanced Brightness Temperature Product (L1C_TB_E). The L1C_TB_E product, posted on a 9 km grid, is then used as the primary input to the current operational SMAP baseline soil moisture retrieval algorithm to produce L2_SM_P_E as the final output. Images of the new product reveal enhanced visual features that are not apparent in the standard product. Based on in situ data from core validation sites and sparse networks representing different seasons and biomes all over the world, comparisons between L2_SM_P_E and in situ data were performed for the duration of April 1, 2015–October 30, 2016. It was found that the performance of the enhanced 9 km L2_SM_P_E is equivalent to that of the standard 36 km L2_SM_P, attaining a retrieval uncertainty below 0.040 m3/m3 unbiased root-mean-square error (ubRMSE) and a correlation coefficient above 0.800. This assessment also affirmed that the Single Channel Algorithm using the V-polarized TB channel (SCA-V) delivered the best retrieval performance among the various algorithms implemented for L2_SM_P_E, a result similar to a previous assessment for L2_SM_P.

Original languageEnglish
JournalRemote Sensing of Environment
Volume204
Pages (from-to)931-941
Number of pages11
ISSN0034-4257
DOIs
StatePublished - 2018
Externally publishedYes
CitationsWeb of Science® Times Cited: 4

    Keywords

  • Assessment, Enhanced, Passive, Retrieval, SMAP, Soil moisture, Validation
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