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moisture products at sites in southwestern France
M. El Hajj, N. Baghdadi, Mehrez Zribi, Nemesio Rodriguez-fernandez, J.P.
Wigneron, A. Al-Yaari, Al Bitar Ahmad, C. Albergel, J.C. Calvet
To cite this version:
M. El Hajj, N. Baghdadi, Mehrez Zribi, Nemesio Rodriguez-fernandez, J.P. Wigneron, et al.. Evalua- tion of SMOS, SMAP, ASCAT and Sentinel-1 soil moisture products at sites in southwestern France.
Remote Sensing, MDPI, 2018, 10 (4), 17 p. �10.3390/rs10040569�. �hal-01900522�
Article
Evaluation of SMOS, SMAP, ASCAT and Sentinel-1 Soil Moisture Products at Sites in
Southwestern France
Mohammad El Hajj
1,*, Nicolas Baghdadi
1ID, Mehrez Zribi
2 ID,
Nemesio Rodríguez-Fernández
2ID, Jean Pierre Wigneron
3, Amen Al-Yaari
3 ID, Ahmad Al Bitar
2ID, Clément Albergel
4 IDand Jean-Christophe Calvet
4ID1
IRSTEA, University of Montpellier, TETIS, 500 rue François Breton, 34093 Montpellier CEDEX 5, France;
nicolas.baghdadi@teledetection.fr
2
Centre d’Etudes Spatiales de la BIOsphère (CESBIO), Université de Toulouse, CNES/CNRS/IRD/UPS, 18 av. Edouard Belin, bpi 2801, 31401 Toulouse CEDEX 9, France; mehrez.zribi@ird.fr (M.Z.);
nemesio.rodriguez@cesbio.cnes.fr (N.R.-F.); ahmad.albitar@cesbio.cnes.fr (A.A.B.)
3
INRA, UMR1391 ISPA, Centre INRA Bordeaux Aquitaine, 33140 Villenave-d’Ornon, France;
jean-pierre.wigneron@inra.fr (J.P.W.); amen.al-yaari@inra.fr (A.A.-Y.)
4
CNRM UMR 3589, Météo-France/CNRS, 31057 Toulouse, France; clement.albergel@meteo.fr (C.A.);
jean-christophe.calvet@meteo.fr (J.-C.C.)
* Correspondence: mohammad.el-hajj@teledetection.fr
Received: 14 February 2018; Accepted: 3 March 2018; Published: 7 April 2018
Abstract: This study evaluates the accuracy of several recent remote sensing Surface Soil Moisture (SSM) products at sites in southwestern France. The products used are Soil Moisture Active Passive
“SMAP” (level 3: 36 km × 36 km, level 3 enhanced: 9 km × 9 km, and Level 2 SMAP/Sentinel-1:
1 km × 1km), Advanced Scatterometer “ASCAT” (level 2 with three spatial resolution 25 km × 25 km, 12.5 km × 12.5 km, and 1 km × 1 km), Soil Moisture and Ocean Salinity “SMOS” (SMOS INRA-CESBIO “SMOS-IC”, SMOS Near-Real-Time “SMOS-NRT”, SMOS Centre Aval de Traitement des Données SMOS level 3 “SMOS-CATDS”, 25 km × 25 km) and Sentinel-1(S1) (25 km × 25 km, 9 km × 9 km, and 1 km × 1 km). The accuracy of SSM products was computed using in situ measurements of SSM observed at a depth of 5 cm. In situ measurements were obtained from the SMOSMANIA ThetaProbe (Time Domaine reflectometry) network (7 stations between 1 January 2016 and 30 June 2017) and additional field campaigns (near Montpellier city in France, between 1 January 2017 and 31 May 2017) in southwestern France. For our study sites, results showed that (i) the accuracy of the Level 2 SMAP/Sentinel-1 was lower than that of SMAP-36 km and SMAP-9 km; (ii) the SMAP-36 km and SMAP-9 km products provide more precise SSM estimates than SMOS products (SMOS-IC, SMOS-NRT, and SMOS-CATDS), mainly due to higher sensitivity of SMOS to RFI (Radio Frequency Interference) noise; and (iii) the accuracy of SMAP-36 km and SMAP-9 km products was similar to that of ASCAT (ASCAT-25 km, ASCAT-12.5 km and ASCAT-1 km) and S1 (S1-25 km, S1-9 km, and S1-1 km) products. The accuracy of SMAP, Sentinel-1 and ASCAT SSM products calculated using the average of statistics obtained on each site is defined by a bias of about
− 3.2 vol. %, RMSD (Root Mean Square Difference) about 7.6 vol. %, ubRMSD (unbiased Root Mean Square Difference)about 5.6 vol. %, and R coefficient about 0.57. For SMOS products, the station average bias, RMSD, ubRMSD, and R coefficient were about − 10.6 vol. %, 12.7 vol. %, 5.9 vol. %, and 0.49, respectively.
Keywords: SMOS; SMAP; ASCAT; Sentinel-1; in situ soil moisture; southwestern France
Remote Sens.2018,10, 569; doi:10.3390/rs10040569 www.mdpi.com/journal/remotesensing