{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,7]],"date-time":"2026-01-07T07:47:59Z","timestamp":1767772079508,"version":"build-2065373602"},"reference-count":43,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2018,4,9]],"date-time":"2018-04-09T00:00:00Z","timestamp":1523232000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"INSU","award":["PNTS PRHYS"],"award-info":[{"award-number":["PNTS PRHYS"]}]},{"DOI":"10.13039\/501100002830","name":"CNES","doi-asserted-by":"publisher","award":["OSTST PRIAM"],"award-info":[{"award-number":["OSTST PRIAM"]}],"id":[{"id":"10.13039\/501100002830","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Radar altimetry provides information on the topography of the Earth surface. It is commonly used for the monitoring not only sea surface height but also ice sheets topography and inland water levels. The radar altimetry backscattering coefficient, which depends on surface roughness and water content, can be related to surface properties such as surface soil moisture content. In this study, the influence of surface soil moisture on the radar altimetry echo and backscattering coefficient is analyzed over semi-arid areas. A semi-empirical model of the soil\u2019s complex dielectric permittivity that takes into account that small-scale roughness and large-scale topography was developed to simulate the radar echoes. It was validated using waveforms acquired at Ku and Ka-bands by ENVISAT RA-2 and SARAL AltiKa respectively over several sites in Mali. Correlation coefficients ranging from 0.66 to 0.94 at Ku-band and from 0.27 to 0.96 at Ka-band were found. The increase in surface soil moisture from 0.02 to 0.4 (i.e., the typical range of variations in semi-arid areas) increase the backscattering from 10 to 15 dB between the core of the dry and the maximum of the rainy seasons.<\/jats:p>","DOI":"10.3390\/rs10040582","type":"journal-article","created":{"date-parts":[[2018,4,10]],"date-time":"2018-04-10T13:06:08Z","timestamp":1523365568000},"page":"582","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["Impact of Surface Soil Moisture Variations on Radar Altimetry Echoes at Ku and Ka Bands in Semi-Arid Areas"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9059-9878","authenticated-orcid":false,"given":"Christophe","family":"Fatras","sequence":"first","affiliation":[{"name":"Office National d\u2019Etudes et de Recherches Aerospatiales (ONERA), 2 Avenue Edouard Belin, 31055 Toulouse CEDEX 4, France"},{"name":"Geosciences Environnement Toulouse (GET), UMR 5563, CNRS\/IRD\/UPS, Observatoire Midi-Pyrenees 8 (OMP), 14 Avenue Edouard Belin, 31400 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pierre","family":"Borderies","sequence":"additional","affiliation":[{"name":"Office National d\u2019Etudes et de Recherches Aerospatiales (ONERA), 2 Avenue Edouard Belin, 31055 Toulouse CEDEX 4, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4661-8274","authenticated-orcid":false,"given":"Fr\u00e9d\u00e9ric","family":"Frappart","sequence":"additional","affiliation":[{"name":"Geosciences Environnement Toulouse (GET), UMR 5563, CNRS\/IRD\/UPS, Observatoire Midi-Pyrenees 8 (OMP), 14 Avenue Edouard Belin, 31400 Toulouse, France"},{"name":"Laboratoire d\u2019Etudes en Geophysique et Oceanographie Spatiales (LEGOS), UMR 5566, CNRS\/IRD\/UPS, Observatoire Midi-Pyrenees 8 (OMP), 14 Avenue Edouard Belin, 31400 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7569-5906","authenticated-orcid":false,"given":"Eric","family":"Mougin","sequence":"additional","affiliation":[{"name":"Geosciences Environnement Toulouse (GET), UMR 5563, CNRS\/IRD\/UPS, Observatoire Midi-Pyrenees 8 (OMP), 14 Avenue Edouard Belin, 31400 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Denis","family":"Blumstein","sequence":"additional","affiliation":[{"name":"Laboratoire d\u2019Etudes en Geophysique et Oceanographie Spatiales (LEGOS), UMR 5566, CNRS\/IRD\/UPS, Observatoire Midi-Pyrenees 8 (OMP), 14 Avenue Edouard Belin, 31400 Toulouse, France"},{"name":"Centre National d\u2019Etudes Spatiales (CNES), 18 Avenue Edouard Belin, 31400 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7475-6017","authenticated-orcid":false,"given":"Fernando","family":"Ni\u00f1o","sequence":"additional","affiliation":[{"name":"Laboratoire d\u2019Etudes en Geophysique et Oceanographie Spatiales (LEGOS), UMR 5566, CNRS\/IRD\/UPS, Observatoire Midi-Pyrenees 8 (OMP), 14 Avenue Edouard Belin, 31400 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2018,4,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1138","DOI":"10.1126\/science.1100217","article-title":"GLACE Team Regions of strong coupling between soil moisture and precipitation","volume":"305","author":"Koster","year":"2004","journal-title":"Science"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/0309-1708(94)90022-1","article-title":"Analytical framework for the characterization of the space-time variability of soil moisture","volume":"17","author":"Entekhabi","year":"1994","journal-title":"Adv. Water Resour."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Small, E.E., and Kurc, S.A. (2003). Tight coupling between soil moisture and the surface radiation budget in semiarid environments: Implications for land-atmosphere interactions. Water Resour. Res., 39.","DOI":"10.1029\/2002WR001297"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"699","DOI":"10.2307\/2258950","article-title":"Factors Affecting Seed Germination in Three Annual Species from an Arid Region of Western Australia","volume":"62","author":"Mott","year":"1974","journal-title":"J. Ecol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"3253","DOI":"10.5194\/bg-12-3253-2015","article-title":"Modelling the effect of soil moisture and organic matter degradation on biogenic NO emissions from soils in Sahel rangeland (Mali)","volume":"12","author":"Delon","year":"2015","journal-title":"Biogeosciences"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1016\/S0034-4257(99)00036-X","article-title":"A Method for Estimating Soil Moisture from ERS Scatterometer and Soil Data","volume":"70","author":"Wagner","year":"1999","journal-title":"Remote Sens. Environ."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"404","DOI":"10.1016\/S0034-4257(02)00015-9","article-title":"Analysis of ERS wind scatterometer time series over Sahel (Mali)","volume":"81","author":"Jarlan","year":"2002","journal-title":"Remote Sens. Environ."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Gruhier, C., de Rosnay, P., Kerr, Y., Mougin, E., Ceschia, E., Calvet, J.C., and Richaume, P. (2008). Evaluation of AMSR-E soil moisture product based on ground measurements over temperate and semi-arid regions. Geophys. Res. Lett., 35.","DOI":"10.1029\/2008GL033330"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"141","DOI":"10.5194\/hess-14-141-2010","article-title":"Soil moisture active and passive microwave products: Intercomparison and evaluation over a Sahelian site","volume":"14","author":"Gruhier","year":"2010","journal-title":"Hydrol. Earth Syst. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"383","DOI":"10.1016\/j.rse.2014.10.005","article-title":"SMOS soil moisture product evaluation over West-Africa from local to regional scale","volume":"156","author":"Louvet","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1016\/S0034-4257(97)00137-5","article-title":"Observations and Interpretation of Seasonal ERS-1 Wind Scatterometer Data over Northern Sahel (Mali)","volume":"63","author":"Frison","year":"1998","journal-title":"Remote Sens. Environ."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Frison, P.-L., Jarlan, L., and Mougin, E. (2016). Using Satellite Scatterometers to Monitor Continental Surfaces. Land Surface Remote Sensing in Continental Hydrology, Elsevier.","DOI":"10.1016\/B978-1-78548-104-8.50003-6"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"399","DOI":"10.1007\/s10712-008-9044-0","article-title":"Global Soil Moisture Patterns Observed by Space Borne Microwave Radiometers and Scatterometers","volume":"29","author":"Wagner","year":"2008","journal-title":"Surv. Geophys."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1999","DOI":"10.1109\/TGRS.2008.2011617","article-title":"An Improved Soil Moisture Retrieval Algorithm for ERS and METOP Scatterometer Observations","volume":"47","author":"Naeimi","year":"2009","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"479","DOI":"10.1016\/j.rse.2016.09.015","article-title":"Comparison of remotely sensed and modelled soil moisture data sets across Australia","volume":"186","author":"Holgate","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"325","DOI":"10.1016\/S0143-6228(99)00009-0","article-title":"Monitoring soil moisture dynamics using satellite imaging radar in northeastern Jordan","volume":"19","author":"Tansey","year":"1999","journal-title":"Appl. Geogr."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1016\/S0168-1923(00)00189-1","article-title":"Soil moisture evaluation using multi-temporal synthetic aperture radar (SAR) in semiarid rangeland","volume":"105","author":"Moran","year":"2000","journal-title":"Agric. For. Meteorol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"2354","DOI":"10.1109\/TGRS.2007.893824","article-title":"Radar Signatures of Sahelian Surfaces in Mali Using ENVISAT-ASAR Data","volume":"45","author":"Baup","year":"2007","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Baup, F., Mougin, E., De Rosnay, P., Hiernaux, P., Frappart, F., Frison, P.L., Zribi, M., and Viarre, J. (2011). Mapping surface soil moisture over the Gourma mesoscale site (Mali) by using ENVISAT ASAR data. Hydrol. Earth Syst. Sci., 15.","DOI":"10.5194\/hessd-7-7417-2010"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1016\/0034-4257(96)00018-1","article-title":"Radar backscatter characteristics of a desert surface","volume":"57","author":"Ridley","year":"1996","journal-title":"Remote Sens. Environ."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Fatras, C., Frappart, F., Mougin, E., Grippa, M., and Hiernaux, P. (2012). Estimating surface soil moisture over Sahel using ENVISAT radar altimetry. Remote Sens. Environ., 123.","DOI":"10.1016\/j.rse.2012.04.013"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Fatras, C., Frappart, F., Mougin, E., Frison, P.-L., Faye, G., Borderies, P., and Jarlan, L. (2015). Spaceborne altimetry and scatterometry backscattering signatures at C- and Ku-bands over West Africa. Remote Sens. Environ., 159.","DOI":"10.1016\/j.rse.2014.12.005"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Frappart, F., Fatras, C., Mougin, E., Marieu, V., Diepkil\u00e9, A.T., Blarel, F., and Borderies, P. (2015). Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over West Africa. Phys. Chem. Earth, 83\u201384.","DOI":"10.1016\/j.pce.2015.05.001"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Bonnefond, P., Verron, J., Aublanc, J., Babu, K., Berg\u00e9-Nguyen, M., Cancet, M., Chaudhary, A., Cr\u00e9taux, J.-F., Frappart, F., and Haines, B. (2018). The Benefits of the Ka-Band as Evidenced from the SARAL\/AltiKa Altimetric Mission: Quality Assessment and Unique Characteristics of AltiKa Data. Remote Sens., 10.","DOI":"10.3390\/rs10010083"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1016\/j.rse.2017.05.004","article-title":"Inverting surface soil moisture information from satellite altimetry over arid and semi-arid regions","volume":"196","author":"Uebbing","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1290","DOI":"10.1109\/LGRS.2016.2582382","article-title":"Radar Backscattering Coefficient over Bare Soils at Ka-Band Close to Nadir Angle","volume":"13","author":"Fatras","year":"2016","journal-title":"IEEE Geosci. Remote Sens. Lett."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1109\/TGRS.1985.289497","article-title":"Microwave Dielectric Behavior of Wet Soil-Part 1: Empirical Models and Experimental Observations","volume":"23","author":"Hallikainen","year":"1985","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1109\/TGRS.1985.289498","article-title":"Microwave Dielectric Behavior of Wet Soil-Part II: Dielectric Mixing Models","volume":"23","author":"Dobson","year":"1985","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1","DOI":"10.6028\/jres.056.001","article-title":"Dielectric constant of water from 0 to 1000 \u00b0C","volume":"56","author":"Malmberg","year":"1956","journal-title":"J. Res. Natl. Bur. Stand."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"561","DOI":"10.1109\/36.485132","article-title":"Measurement and modeling of the millimeter-wave backscatter response of soil surfaces","volume":"34","author":"Nashashibi","year":"1996","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_31","unstructured":"Fawwaz, T., and Elachi, C. (1990). Radar Polarimetry for Geoscience Applications, Artech House."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Ruck, G.T., Barrick, D.E., Stuart, W.D., and Krichbaum, C.K. (1970). Radar Cross Section Handbook, Plenum Press.","DOI":"10.1007\/978-1-4899-5324-7"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Chelton, D.B., Ries, J.C., Haines, B.J., Fu, L.-L., and Callahan, P.S. (2001). Chapter 1 Satellite Altimetry. Satellite Altimetry and Earth Sciences: A Handbook of Techniques and Applications, Elsevier.","DOI":"10.1016\/S0074-6142(01)80146-7"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1016\/j.asr.2016.10.008","article-title":"Satellite radar altimetry water elevations performance over a 200 m wide river: Evaluation over the Garonne River","volume":"59","author":"Biancamaria","year":"2017","journal-title":"Adv. Space Res."},{"key":"ref_35","unstructured":"(2018, April 09). CTOH (Center for Topographic studies of the Ocean and Hydrosphere). Available online: http:\/\/ctoh.legos.obs-mip.fr."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"323","DOI":"10.1016\/S0094-5765(99)00063-6","article-title":"ENVISAT RA-2 advanced radar altimeter: Instrument design and pre-launch performance assessment review","volume":"44","author":"Zelli","year":"1999","journal-title":"Acta Astronaut."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Tachikawa, T., Hato, M., Kaku, M., and Iwasaki, A. (2011, January 24\u201329). The characteristics of ASTER GDEM version 2. Proceedings of the IEEE International Geoscience and Remote Sensing Symposium, Vancouver, BC, Canada.","DOI":"10.1109\/IGARSS.2011.6050017"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1080\/01490419.2014.988835","article-title":"AltiKa Altimeter: Instrument Description and In Flight Performance","volume":"38","author":"Steunou","year":"2015","journal-title":"Mar. Geod."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Mougin, E., Hiernaux, P., Kergoat, L., Grippa, M., de Rosnay, P., Timouk, F., Le Dantec, V., Demarez, V., Lavenu, F., and Arjounin, M. (2009). The AMMA-CATCH Gourma observatory site in Mali: Relating climatic variations to changes in vegetation, surface hydrology, fluxes and natural resources. J. Hydrol., 375.","DOI":"10.1016\/j.jhydrol.2009.06.045"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1016\/j.jhydrol.2009.03.007","article-title":"Rainfall regime across the Sahel band in the Gourma region, Mali","volume":"375","author":"Frappart","year":"2009","journal-title":"J. Hydrol."},{"key":"ref_41","unstructured":"Wingham, D.J., Rapley, C.G., and Griffiths, H. (1986, January 8\u201311). New Techniques in Satellite Altimeter Tracking Systems. Proceedings of the 1986 International Geoscience and Remote Sensing Symposium on Remote Sensing, Zurich, Switzerland."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Frappart, F., Calmant, S., Cauhop\u00e9, M., Seyler, F., and Cazenave, A. (2006). Preliminary results of ENVISAT RA-2-derived water levels validation over the Amazon basin. Remote Sens. Environ., 100.","DOI":"10.1016\/j.rse.2005.10.027"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"3261","DOI":"10.1002\/2014JC010338","article-title":"Ka-band backscattering from water surface at small incidence: A wind-wave tank study","volume":"120","author":"Boisot","year":"2015","journal-title":"J. Geophys. Res. Oceans"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/4\/582\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:00:07Z","timestamp":1760194807000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/4\/582"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,4,9]]},"references-count":43,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2018,4]]}},"alternative-id":["rs10040582"],"URL":"https:\/\/doi.org\/10.3390\/rs10040582","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2018,4,9]]}}}