{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,28]],"date-time":"2026-02-28T04:30:28Z","timestamp":1772253028866,"version":"3.50.1"},"reference-count":57,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2018,12,7]],"date-time":"2018-12-07T00:00:00Z","timestamp":1544140800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The snow melt from the High Atlas is a critical water resource in Morocco. In spite of its importance, monitoring the spatio-temporal evolution of key snow cover properties like the snow water equivalent remains challenging due to the lack of in situ measurements at high elevation. Since 2015, the Sentinel-2 mission provides high spatial resolution images with a 5 day revisit time, which offers new opportunities to characterize snow cover distribution in mountain regions. Here we present a new data assimilation scheme to estimate the state of the snowpack without in situ data. The model was forced using MERRA-2 data and a particle filter was developed to dynamically reduce the biases in temperature and precipitation using Sentinel-2 observations of the snow cover area. The assimilation scheme was implemented using SnowModel, a distributed energy-balance snowpack model and tested in a pilot catchment in the High Atlas. The study period covers 2015\u20132016 snow season which corresponds to the first operational year of Sentinel-2A, therefore the full revisit capacity was not yet achieved. Yet, we show that the data assimilation led to a better agreement with independent observations of the snow height at an automatic weather station and the snow cover extent from MODIS. The performance of the data assimilation scheme should benefit from the continuous improvements of MERRA-2 reanalysis and the full revisit capacity of Sentinel-2.<\/jats:p>","DOI":"10.3390\/rs10121982","type":"journal-article","created":{"date-parts":[[2018,12,10]],"date-time":"2018-12-10T03:36:41Z","timestamp":1544413001000},"page":"1982","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":22,"title":["Assimilation of Sentinel-2 Data into a Snowpack Model in the High Atlas of Morocco"],"prefix":"10.3390","volume":"10","author":[{"given":"Mohamed Wassim","family":"Baba","sequence":"first","affiliation":[{"name":"Centre d\u2019Etudes Spatiales de la Biosph\u00e8re, Universit\u00e9 de Toulouse, CNRS\/CNES\/IRD\/INRA\/UPS, 18 av. E. Belin bpi 2801, 31401 Toulouse, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4996-6768","authenticated-orcid":false,"given":"Simon","family":"Gascoin","sequence":"additional","affiliation":[{"name":"Centre d\u2019Etudes Spatiales de la Biosph\u00e8re, Universit\u00e9 de Toulouse, CNRS\/CNES\/IRD\/INRA\/UPS, 18 av. E. Belin bpi 2801, 31401 Toulouse, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3756-0944","authenticated-orcid":false,"given":"Lahoucine","family":"Hanich","sequence":"additional","affiliation":[{"name":"Laboratoire G\u00e9oressources-D\u00e9partement des Sciences de la Terre, Facult\u00e9 des Sciences et Techniques Gu\u00e9liz, Universit\u00e9 Cadi Ayyad, av. A. Khattabi, BP 549, Marrakech 40000, Morocco"}]}],"member":"1968","published-online":{"date-parts":[[2018,12,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Viviroli, D., D\u00fcrr, H.H., Messerli, B., Meybeck, M., and Weingartner, R. (2007). Mountains of the world, water towers for humanity: Typology, mapping, and global significance. Water Resour. Res., 43.","DOI":"10.1029\/2006WR005653"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1076","DOI":"10.5194\/hess-8-1076-2004","article-title":"Snowmelt and sublimation: Field experiments and modelling in the High Atlas Mountains of Morocco","volume":"8","author":"Schulz","year":"2004","journal-title":"Hydrol. Earth Syst. Sci."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1094","DOI":"10.1623\/hysj.54.6.1094","article-title":"Evaluation of the snowmelt runoff model in the Moroccan High Atlas Mountains using two snow-cover estimates","volume":"54","author":"Boudhar","year":"2009","journal-title":"Hydrol. Sci. J."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Baba, M., Gascoin, S., Jarlan, L., Simonneaux, V., and Hanich, L. (2018). Variations of the Snow Water Equivalent in the Ourika Catchment (Morocco) over 2000\u20132018 Using Downscaled MERRA-2 Data. Water, 10.","DOI":"10.3390\/w10091120"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"573","DOI":"10.5194\/essd-9-573-2017","article-title":"Snow observations in Mount Lebanon (2011\u20132016)","volume":"9","author":"Fayad","year":"2017","journal-title":"Earth Syst. Sci. Data"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1935","DOI":"10.1002\/(SICI)1099-1085(199909)13:12\/13<1935::AID-HYP868>3.0.CO;2-C","article-title":"A spatially distributed energy balance snowmelt model for application in mountain basins","volume":"13","author":"Marks","year":"1999","journal-title":"Hydrol. Process."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"505","DOI":"10.1007\/s11707-017-0641-4","article-title":"Spatio-temporal snowmelt variability across the headwaters of the Southern Rocky Mountains","volume":"11","author":"Fassnacht","year":"2017","journal-title":"Front. Earth Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"72","DOI":"10.1016\/j.rse.2015.01.002","article-title":"Assessment of daily MODIS snow cover products to monitor snow cover dynamics over the Moroccan Atlas mountain range","volume":"160","author":"Marchane","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"461","DOI":"10.1002\/wat2.1140","article-title":"Estimating the spatial distribution of snow water equivalent in the world\u2019s mountains","volume":"3","author":"Dozier","year":"2016","journal-title":"Wiley Interdiscip. Rev. Water"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"5419","DOI":"10.1175\/JCLI-D-16-0758.1","article-title":"The Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2)","volume":"30","author":"Gelaro","year":"2017","journal-title":"J. Clim."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Durand, M., Molotch, N.P., and Margulis, S.A. (2008). A Bayesian approach to snow water equivalent reconstruction. J. Geophys. Res. Atmos., 113.","DOI":"10.1029\/2008JD009894"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1680","DOI":"10.1002\/joc.4804","article-title":"The Andes Cordillera. Part I: Snow distribution, properties, and trends (1979\u20132014)","volume":"37","author":"Mernild","year":"2017","journal-title":"Int. J. Climatol."},{"key":"ref_13","first-page":"19250","article-title":"Contribution of high resolution remote sensing data to the modeling of the snow cover the in Atlas Mountains","volume":"Volume 19","author":"Baba","year":"2017","journal-title":"EGU General Assembly Conference Abstracts"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1643","DOI":"10.1175\/JCLI-D-16-0570.1","article-title":"Land surface precipitation in MERRA-2","volume":"30","author":"Reichle","year":"2017","journal-title":"J. Clim."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"4094","DOI":"10.1080\/01431161.2011.640964","article-title":"Remote sensing of snow\u2014A review of available methods","volume":"33","author":"Dietz","year":"2012","journal-title":"Int. J. Remote Sens."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Dumont, M., and Gascoin, S. (2017). Optical remote sensing of snow cover. Land Surface Remote Sensing in Continental Hydrology, Elsevier.","DOI":"10.1016\/B978-1-78548-104-8.50004-8"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"872","DOI":"10.1016\/j.advwatres.2005.08.004","article-title":"Assimilating remotely sensed snow observations into a macroscale hydrology model","volume":"29","author":"Andreadis","year":"2006","journal-title":"Adv. Water Resour."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1309","DOI":"10.1016\/j.advwatres.2008.06.005","article-title":"Hydrological data assimilation with the ensemble Kalman filter: Use of streamflow observations to update states in a distributed hydrological model","volume":"31","author":"Clark","year":"2008","journal-title":"Adv. Water Resour."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"130","DOI":"10.1175\/2008JHM1042.1","article-title":"Forward-looking assimilation of MODIS-derived snow-covered area into a land surface model","volume":"10","author":"Zaitchik","year":"2009","journal-title":"J. Hydrometeorol."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"De Lannoy, G.J., Reichle, R.H., Arsenault, K.R., Houser, P.R., Kumar, S., Verhoest, N.E., and Pauwels, V.R. (2012). Multiscale assimilation of Advanced Microwave Scanning Radiometer\u2014EOS snow water equivalent and Moderate Resolution Imaging Spectroradiometer snow cover fraction observations in northern Colorado. Adv. Water Resour., 48.","DOI":"10.1029\/2011WR010588"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"5825","DOI":"10.3390\/rs5115825","article-title":"Assimilation of MODIS snow cover area data in a distributed hydrological model using the particle filter","volume":"5","author":"Thirel","year":"2013","journal-title":"Remote Sens."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1752","DOI":"10.1175\/JHM-D-14-0177.1","article-title":"A particle batch smoother approach to snow water equivalent estimation","volume":"16","author":"Margulis","year":"2015","journal-title":"J. Hydrometeorol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1647","DOI":"10.5194\/tc-11-1647-2017","article-title":"Assimilation of snow cover and snow depth into a snow model to estimate snow water equivalent and snowmelt runoff in a Himalayan catchment","volume":"11","author":"Stigter","year":"2017","journal-title":"Cryosphere"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Toure, A.M., Reichle, R.H., Forman, B.A., Getirana, A., and De Lannoy, G.J. (2018). Assimilation of MODIS Snow Cover Fraction Observations into the NASA Catchment Land Surface Model. Remote Sens., 10.","DOI":"10.3390\/rs10020316"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"6859","DOI":"10.1002\/2017GL073826","article-title":"Impacts of El Ni\u00f1o and La Ni\u00f1a on interannual snow accumulation in the Andes: Results from a high-resolution 31 year reanalysis","volume":"44","author":"Margulis","year":"2017","journal-title":"Geophys. Res. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"2337","DOI":"10.5194\/hess-19-2337-2015","article-title":"A snow cover climatology for the Pyrenees from MODIS snow products","volume":"19","author":"Gascoin","year":"2015","journal-title":"Hydrol. Earth Syst. Sci."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Gascon, F., Bouzinac, C., Th\u00e9paut, O., Jung, M., Francesconi, B., Louis, J., Lonjou, V., Lafrance, B., Massera, S., and Gaudel-Vacaresse, A. (2017). Copernicus Sentinel-2A calibration and products validation status. Remote Sens., 9.","DOI":"10.3390\/rs9060584"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/j.rse.2011.11.026","article-title":"Sentinel-2: ESA\u2019s optical high-resolution mission for GMES operational services","volume":"120","author":"Drusch","year":"2012","journal-title":"Remote Sens. Environ."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1259","DOI":"10.1175\/JHM548.1","article-title":"A distributed snow-evolution modeling system (SnowModel)","volume":"7","author":"Liston","year":"2006","journal-title":"J. Hydrometeorol."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Moradkhani, H., Hsu, K.L., Gupta, H., and Sorooshian, S. (2005). Uncertainty assessment of hydrologic model states and parameters: Sequential data assimilation using the particle filter. Adv. Water Resour., 41.","DOI":"10.1029\/2004WR003604"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"253","DOI":"10.1007\/s00477-010-0445-5","article-title":"Snow water equivalent prediction using Bayesian data assimilation methods","volume":"25","author":"Leisenring","year":"2011","journal-title":"Stoch. Environ. Res. Risk Assess."},{"key":"ref_32","unstructured":"van Leeuwen, P.J., K\u00fcnsch, H.R., Nerger, L., Potthast, R., and Reich, S. (arXiv, 2018). Particle filters for applications in geosciences, arXiv."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"4879","DOI":"10.1080\/01431161.2015.1093198","article-title":"Remote sensing of water resources in semi-arid mediterranean areas: The joint international laboratory TREMA","volume":"36","author":"Jarlan","year":"2015","journal-title":"Int. J. Remote Sens."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"979","DOI":"10.1080\/02626667.2017.1283042","article-title":"Climate change impacts on surface water resources in the Rheraya catchment (High Atlas, Morocco)","volume":"62","author":"Marchane","year":"2017","journal-title":"Hydrol. Sci. J."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1051\/lhb\/2018032","article-title":"Mod\u00e9lisation pluie-d\u00e9bit et analyse du r\u00e9gime d\u2019un bassin versant semi-aride sous influence nivale. Cas du bassin versant du Rheraya (Haut Atlas, Maroc)","volume":"3","author":"Hajhouji","year":"2018","journal-title":"La Houille Blanche"},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Baba, M.W., Gascoin, S., Kinnard, C., Marchane, A., and Hanich, L. (2018, December 04). Effect of Digital Elevation Model Resolution on the Simulation of the Snow Cover Evolution in the High Atlas. Available online: https:\/\/osf.io\/9zxqg\/.","DOI":"10.31219\/osf.io\/9zxqg"},{"key":"ref_37","first-page":"1","article-title":"Theia Snow collection: high resolution operational snow cover maps from Sentinel-2 and Landsat-8 data","volume":"2018","author":"Gascoin","year":"2018","journal-title":"Earth Syst. Sci. Data Discuss."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Lonjou, V., Desjardins, C., Hagolle, O., Petrucci, B., Tremas, T., Dejus, M., Makarau, A., and Auer, S. (2016, January 26\u201329). MACCS-ATCOR joint algorithm (MAJA). Proceedings of the Remote Sensing of Clouds and the Atmosphere XXI, Edinburgh, UK.","DOI":"10.1117\/12.2240935"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1016\/0034-4257(89)90101-6","article-title":"Spectral signature of alpine snow cover from the Landsat Thematic Mapper","volume":"28","author":"Dozier","year":"1989","journal-title":"Remote Sens. Environ."},{"key":"ref_40","unstructured":"Hall, D.K., Riggs, G.A., Salomonson, V.V., Barton, J., Casey, K., Chien, J., DiGirolamo, N., Klein, A., Powell, H., and Tait, A. (2001). Algorithm Theoretical Basis Document (ATBD) for the MODIS Snow and Sea Ice-Mapping Algorithms. Nasa Gsfc, 45. Available online: https:\/\/eospso.gsfc.nasa.gov\/sites\/default\/files\/atbd\/atbd_mod10.pdf."},{"key":"ref_41","unstructured":"Baldo, E. (2017). Towards Large-Scale Implementation of a High Resolution Snow Reanalysis over Midlatitude Montane Ranges. [Ph.D. Thesis, University of California]."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1908","DOI":"10.1002\/hyp.6775","article-title":"Understanding hydrological processes with scarce data in a mountain environment","volume":"22","author":"Boulet","year":"2008","journal-title":"Hydrol. Process."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"217","DOI":"10.1175\/JHM486.1","article-title":"A meteorological distribution system for high-resolution terrestrial modeling (MicroMet)","volume":"7","author":"Liston","year":"2006","journal-title":"J. Hydrometeorol."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"8437","DOI":"10.1002\/2016WR018704","article-title":"Validating reconstruction of snow water equivalent in California\u2019s Sierra Nevada using measurements from the NASA Airborne Snow Observatory","volume":"52","author":"Bair","year":"2016","journal-title":"Adv. Water Resour."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"241","DOI":"10.3189\/172756507782202865","article-title":"Simulating complex snow distributions in windy environments using SnowTran-3D","volume":"53","author":"Liston","year":"2007","journal-title":"J. Glaciol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"396","DOI":"10.1175\/1520-0450(1964)003<0396:ATFMDI>2.0.CO;2","article-title":"A technique for maximizing details in numerical weather map analysis","volume":"3","author":"Barnes","year":"1964","journal-title":"J. Appl. Meteorol."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1016\/j.advwatres.2012.11.013","article-title":"Wind effects on snow cover in Pascua-Lama, Dry Andes of Chile","volume":"55","author":"Gascoin","year":"2013","journal-title":"Adv. Water Resour."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"685","DOI":"10.1175\/JHM-D-13-073.1","article-title":"Sensitivity of precipitation phase over the Swiss Alps to different meteorological variables","volume":"15","author":"Froidurot","year":"2014","journal-title":"J. Hydrometeorol."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"1568","DOI":"10.3390\/rs5041568","article-title":"Snow cover maps from MODIS images at 250 m resolution, part 2: Validation","volume":"5","author":"Notarnicola","year":"2013","journal-title":"Remote Sens."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"1381","DOI":"10.1175\/1520-0442(2004)017<1381:RSSCHI>2.0.CO;2","article-title":"Representing subgrid snow cover heterogeneities in regional and global models","volume":"17","author":"Liston","year":"2004","journal-title":"J. Clim."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"985","DOI":"10.1175\/JHM450.1","article-title":"Twentieth-century drought in the conterminous United States","volume":"6","author":"Andreadis","year":"2005","journal-title":"J. Hydrometeorol."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"1991","DOI":"10.1002\/qj.699","article-title":"Nonlinear data assimilation in geosciences: An extremely efficient particle filter","volume":"136","year":"2010","journal-title":"Q. J. R. Meteorol. Soc."},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Douc, R., and Capp\u00e9, O. (2005, January 15\u201317). Comparison of resampling schemes for particle filtering. Proceedings of the 4th International Symposium on the Image and Signal Processing and Analysis, Zagreb, Croatia.","DOI":"10.1109\/ISPA.2005.195385"},{"key":"ref_54","unstructured":"Pencheva, T., Atanassov, K., and Shannon, A. (2009, January 5). Modelling of a stochastic universal sampling selection operator in genetic algorithms using generalized nets. Proceedings of the Tenth International Workshop on Generalized Nets, Sofia, Bulgaria."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"3237","DOI":"10.5194\/hess-15-3237-2011","article-title":"Applying sequential Monte Carlo methods into a distributed hydrologic model: Lagged particle filtering approach with regularization","volume":"15","author":"Noh","year":"2011","journal-title":"Hydrol. Earth Syst. Sci."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"1021","DOI":"10.5194\/tc-10-1021-2016","article-title":"On the assimilation of optical reflectances and snow depth observations into a detailed snowpack model","volume":"10","author":"Charrois","year":"2016","journal-title":"Cryosphere"},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"247","DOI":"10.5194\/tc-12-247-2018","article-title":"Ensemble-based assimilation of fractional snow-covered area satellite retrievals to estimate the snow distribution at Arctic sites","volume":"17","author":"Aalstad","year":"2018","journal-title":"Cryosphere"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/12\/1982\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:32:06Z","timestamp":1760196726000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/12\/1982"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,12,7]]},"references-count":57,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2018,12]]}},"alternative-id":["rs10121982"],"URL":"https:\/\/doi.org\/10.3390\/rs10121982","relation":{"has-preprint":[{"id-type":"doi","id":"10.20944\/preprints201810.0264.v1","asserted-by":"object"}]},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,12,7]]}}}