Journal cover Journal topic
Earth System Science Data The Data Publishing Journal
Earth Syst. Sci. Data, 9, 293-315, 2017
https://doi.org/10.5194/essd-9-293-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Review article
06 Jun 2017
The global SMOS Level 3 daily soil moisture and brightness temperature maps
Ahmad Al Bitar1,2, Arnaud Mialon1,2, Yann H. Kerr1,3, François Cabot1,3, Philippe Richaume1, Elsa Jacquette3, Arnaud Quesney4, Ali Mahmoodi1, Stéphane Tarot5, Marie Parrens1, Amen Al-Yaari6, Thierry Pellarin7, Nemesio Rodriguez-Fernandez1, and Jean-Pierre Wigneron6 1Centre d'Etudes Spatiales de la Biosphère, Université de Toulouse, CNES/CNRS/IRD/UPS, Toulouse, France
2Centre National de Recherche Scientifique, Paris, France
3Centre National d'Etudes Spatiales, Paris, France
4CapGemini Sud, 109 Avenue du Général Eisenhower, 31000 Toulouse, France
5IFremer, BP 70, 29280 Plouzane, France
6INRA, UMR1391 ISPA, Villenave d'Ornon, France
7IGE, University Grenoble Alpes, CNRS/G-INP/IRD/UGA, Grenoble, France
Abstract. The objective of this paper is to present the multi-orbit (MO) surface soil moisture (SM) and angle-binned brightness temperature (TB) products for the SMOS (Soil Moisture and Ocean Salinity) mission based on a new multi-orbit algorithm. The Level 3 algorithm at CATDS (Centre Aval de Traitement des Données SMOS) makes use of MO retrieval to enhance the robustness and quality of SM retrievals. The motivation of the approach is to make use of the longer temporal autocorrelation length of the vegetation optical depth (VOD) compared to the corresponding SM autocorrelation in order to enhance the retrievals when an acquisition occurs at the border of the swath. The retrieval algorithm is implemented in a unique operational processor delivering multiple parameters (e.g. SM and VOD) using multi-angular dual-polarisation TB from MO. A subsidiary angle-binned TB product is provided. In this study the Level 3 TB V310 product is showcased and compared to SMAP (Soil Moisture Active Passive) TB. The Level 3 SM V300 product is compared to the single-orbit (SO) retrievals from the Level 2 SM processor from ESA with aligned configuration. The advantages and drawbacks of the Level 3 SM product (L3SM) are discussed. The comparison is done on a global scale between the two datasets and on the local scale with respect to in situ data from AMMA-CATCH and USDA ARS Watershed networks. The results obtained from the global analysis show that the MO implementation enhances the number of retrievals: up to 9 % over certain areas. The comparison with the in situ data shows that the increase in the number of retrievals does not come with a decrease in quality, but rather at the expense of an increased time lag in product availability from 6 h to 3.5 days, which can be a limiting factor for applications like flood forecast but reasonable for drought monitoring and climate change studies. The SMOS L3 soil moisture and L3 brightness temperature products are delivered using an open licence and free of charge using a web application (https://www.catds.fr/sipad/). The RE04 products, versions 300 and 310, used in this paper are also available at ftp://ext-catds-cpdc:catds2010@ftp.ifremer.fr/Land_products/GRIDDED/L3SM/RE04/.

Citation: Al Bitar, A., Mialon, A., Kerr, Y. H., Cabot, F., Richaume, P., Jacquette, E., Quesney, A., Mahmoodi, A., Tarot, S., Parrens, M., Al-Yaari, A., Pellarin, T., Rodriguez-Fernandez, N., and Wigneron, J.-P.: The global SMOS Level 3 daily soil moisture and brightness temperature maps, Earth Syst. Sci. Data, 9, 293-315, https://doi.org/10.5194/essd-9-293-2017, 2017.
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Short summary
Surface soil moisture is a control variable for many processes linked to the water and carbon cycles. The global maps of soil moisture and brightness temperature using multiple orbits from the SMOS (Soil Moisture and Ocean Salinity) mission are presented in this paper. The maps showed an increased number of retrievals over forest areas (9 %) compared to single-orbit retrievals. The brightness temperature observations from the L-band missions SMOS (ESA) and SMAP (NASA) are close (bias < −4 K).
Surface soil moisture is a control variable for many processes linked to the water and carbon...
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