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1. Validation of NASA SMAP Satellite Soil Moisture Products over the Desert of Kuwait

Author

Hala AlJassar, Marouane Temimi, Mohamed Abdelkader, Peter Petrov, Panagiotis Kokkalis, Hussain AlSarraf, Nair Roshni, and Hamad Al Hendi

Subjects
SMAP, validation, volumetric soil moisture (VSM), desert, Kuwait, Science
Abstract

The goal of this study is to validate and analyze NASA’s Soil Moisture Active Passive (SMAP) products over the desert of Kuwait. The study period was between April 2015 and April 2020. The study domain includes a mission candidate calibration/validation (Cal/Val) site that comprises six permanent soil moisture stations used to verify SMAP estimates. In addition, intensive field campaigns were conducted within and around the candidate Cal/Val site during the study period to collect additional thermogravimetric samples. The mean difference (MD), root mean squared difference (RMSD), unbiased root mean square difference (ubRMSD), and correlation coefficient (R) were computed to assess the agreement between SMAP SM products and in situ observations. The comparison of the six ground station sensors’ observations with the thermogravimetric samples led to an absolute mean bias (AMB) of 0.034 m3 m−3, which was then used to calibrate the sensors and bias-correct their measurements. The temporal consistency of the readings from the test site and calibrated sensors was assessed using the mean relative difference (MRD) and its standard deviation of relative difference (SDRD). Using a sampling density analysis, it was determined that a minimum of four ground stations would be required to validate the test site. Furthermore, the consistency between SMAP satellite soil moisture data and those derived from the Soil Moisture and Ocean Salinity (SMOS) satellite operated by the European Space Agency, and their agreement with in situ samples, was analyzed. The comparison of SMAP and SMOS soil moisture data with in situ observations showed that both satellites successfully captured the spatial and temporal distribution of soil moisture. For SMAP and SMOS, the lowest ubRMSE statistics were 0.043 m3 m−3 and 0.045 m3 m−3, respectively, which are slightly higher than the mission target of 0.04 m3 m−3.

Published
2022
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2. Validation of Soil Moisture Data Products From the NASA SMAP Mission

Author

Fan Chen, Simon Yueh, Scott Dunbar, Yijian Zeng, Zhongbo Su, Jean-Christophe Calvet, Julian Chaubell, Mehrez Zribi, Peggy O'Neill, Isabella Pfeil, Narendra N. Das, Ernesto Lopez-Baeza, Rolf H. Reichle, M. Thibeault, Seung-Bum Kim, Lan Dang, Rajat Bindlish, Jouni Pulliainen, Heather McNairn, Chandra Holifield Collins, Karsten Høgh Jensen, Bimal K. Bhattacharya, Qing Liu, Michael H. Cosh, Judith Ramos, Steven Chan, Jeffrey P. Walker, Hala Aljassar, Mariette Vreugdenhil, Thierry Pellarin, Thomas N. Jackson, Carsten Montzka, Mark Seyfrie, Laura L. Bourgeau-Chavez, Stan Livingston, Todd G. Caldwell, Aaron A. Berg, Mahta Moghaddam, Claudia Notarnicola, David D. Bosch, Andreas Colliander, Wade T. Crow, Dara Entekhabi, Jun Asanuma, John S. Kimball, José Martínez-Fernández, R. van der Velde, Patrick J. Starks, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Centre national de recherches météorologiques (CNRM), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Department of Water Resources, UT-I-ITC-WCC, Faculty of Geo-Information Science and Earth Observation, and CNRS, Univ. Grenoble-Alpes, Institut des Géosciences de l'Environnement (IGE), Grenoble, France (IGE)

Subjects
Atmospheric Science, Data products, 010504 meteorology & atmospheric sciences, Soil Moisture, Geophysics. Cosmic physics, 0211 other engineering and technologies, 02 engineering and technology, 010501 environmental sciences, 010502 geochemistry & geophysics, 01 natural sciences, Satellite broadcasting, Validation, Computers in Earth Sciences, TC1501-1800, Water content, ComputingMilieux_MISCELLANEOUS, Remote sensing, SMAP mission, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Sea surface, validation, QC801-809, soil moisture (SM), SMAP, [SDE.ES]Environmental Sciences/Environmental and Society, Active passive, Ocean engineering, Soil Moisture Active Passive (SMAP), Core Validation Sites, 13. Climate action, Soil measurements, ITC-ISI-JOURNAL-ARTICLE, [SDE]Environmental Sciences, ddc:520, Environmental science, NASA, ITC-GOLD, Core validation sites (CVS)
Abstract

The National Aeronautics and Space Administration Soil Moisture Active Passive (SMAP) mission has been validating its soil moisture (SM) products since the start of data production on March 31, 2015. Prior to launch, the mission defined a set of criteria for core validation sites (CVS) that enable the testing of the key mission SM accuracy requirement (unbiased root-mean-square error 3/m3). The validation approach also includes other (“sparse network”) in situ SM measurements, satellite SM products, model-based SM products, and field experiments. Over the past six years, the SMAP SM products have been analyzed with respect to these reference data, and the analysis approaches themselves have been scrutinized in an effort to best understand the products’ performance. Validation of the most recent SMAP Level 2 and 3 SM retrieval products (R17000) shows that the L-band (1.4 GHz) radiometer-based SM record continues to meet mission requirements. The products are generally consistent with SM retrievals from the European Space Agency Soil Moisture Ocean Salinity mission, although there are differences in some regions. The high-resolution (3-km) SM retrieval product, generated by combining Copernicus Sentinel-1 data with SMAP observations, performs within expectations. Currently, however, there is limited availability of 3-km CVS data to support extensive validation at this spatial scale. The most recent (version 5) SMAP Level 4 SM data assimilation product providing surface and root-zone SM with complete spatio–temporal coverage at 9-km resolution also meets performance requirements. The SMAP SM validation program will continue throughout the mission life; future plans include expanding it to forested and high-latitude regions.

Published
2022
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