{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,29]],"date-time":"2026-05-29T21:54:35Z","timestamp":1780091675291,"version":"3.54.0"},"reference-count":54,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2018,5,15]],"date-time":"2018-05-15T00:00:00Z","timestamp":1526342400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Institutional Research Funding (IUT)","award":["19-6"],"award-info":[{"award-number":["19-6"]}]},{"name":"Personal Research Funding of the Estonian Ministry of Education and Research","award":["PUT1378"],"award-info":[{"award-number":["PUT1378"]}]},{"name":"CMEMS Copernicus","award":["WAVE2NEMO."],"award-info":[{"award-number":["WAVE2NEMO."]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>A method for estimating meteo-marine parameters from satellite Synthetic Aperture Radar (SAR) data, intended for near-real-time (NRT) service over the Baltic Sea, is presented and validated. Total significant wave height data are retrieved with an empirical function CWAVE_S1-IW, which combines spectral analysis of Sentinel-1A\/B Interferometric Wide swath (IW) subscenes with wind data derived with common C-Band Geophysical Model Functions (GMFs). In total, 15 Sentinel-1A\/B scenes (116 acquisitions) over the Baltic Sea were processed for comparison with off-shore sea state measurements (52 collocations) and coastal wind measurements (357 colocations). Sentinel-1 wave height was spatially compared with WAM wave model results (Copernicus Marine Environment Monitoring Service (CMEMS). The comparison of SAR-derived wave heights shows good agreement with measured wave heights correlation r of 0.88 and with WAM model (r = 0.85). The wind speed estimated from SAR images yields good agreement with in situ data (r = 0.91). The study demonstrates that the wave retrievals from Sentinel-1 IW data provide valuable information for operational and statistical monitoring of wave conditions in the Baltic Sea. The data is valuable for model validation and interpretation in regions where, and during periods when, in situ measurements are missing. The Sentinel-1 A\/B wave retrievals provide more detailed information about spatial variability of the wave field in the coastal zone compared to in situ measurements, altimetry wave products and model forecast. Thus, SAR data enables estimation of storm locations and areal coverage. Methods shown in the study are implemented in NRT service in German Aerospace Center\u2019s (DLR) ground station Neustrelitz.<\/jats:p>","DOI":"10.3390\/rs10050757","type":"journal-article","created":{"date-parts":[[2018,5,15]],"date-time":"2018-05-15T11:36:13Z","timestamp":1526384173000},"page":"757","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":27,"title":["Meteo-Marine Parameters from Sentinel-1 SAR Imagery: Towards Near Real-Time Services for the Baltic Sea"],"prefix":"10.3390","volume":"10","author":[{"given":"Sander","family":"Rikka","sequence":"first","affiliation":[{"name":"Department of Marine Systems at Tallinn University of Technology, Tallinn 12618, Estonia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrey","family":"Pleskachevsky","sequence":"additional","affiliation":[{"name":"German Aerospace Center (DLR), Remote Sensing Technology Institute, Bremen 28199, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sven","family":"Jacobsen","sequence":"additional","affiliation":[{"name":"German Aerospace Center (DLR), Remote Sensing Technology Institute, Bremen 28199, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Victor","family":"Alari","sequence":"additional","affiliation":[{"name":"Department of Marine Systems at Tallinn University of Technology, Tallinn 12618, Estonia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rivo","family":"Uiboupin","sequence":"additional","affiliation":[{"name":"Department of Marine Systems at Tallinn University of Technology, Tallinn 12618, Estonia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2018,5,15]]},"reference":[{"key":"ref_1","unstructured":"Lehner, S., Schulz-Stellenfleth, J., Brusch, S., and Li, X.M. (2008, January 26\u201330). Use of TerraSAR-X data for oceanography. Proceedings of the 2008 7th European Conference on Synthetic Aperture Radar (EUSAR), Rome, Italy."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"830","DOI":"10.1109\/TGRS.2009.2033177","article-title":"Investigation of ocean surface wave refraction using TerraSAR-X data","volume":"48","author":"Li","year":"2010","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1761","DOI":"10.1029\/JC088iC03p01761","article-title":"Large-And Small-Scale Spatial Evolution of Digitally Processed Ocean Wave Spectra from SEASAT Synthetic Aperture Radar","volume":"88","author":"Beal","year":"1983","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"13065","DOI":"10.1029\/JC091iC11p13065","article-title":"Measurement of Microwave Backscattering Signatures of the Ocean Surface Using X Band and Ka Band Airborne Scatterometers","volume":"91","author":"Masuko","year":"1986","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_5","unstructured":"Schulz-Stellenfleth, J. (2004). Ocean Wave Measurements Using Complex Synthetic Aperture Radar Data, University of Hamburg."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"10713","DOI":"10.1029\/91JC00302","article-title":"On the Nonlinear Mapping of an Ocean Wave Spectrum into a Synthetic Aperture Radar Image Spectrum and Its Inversion","volume":"96","author":"Hasselmann","year":"1991","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"16615","DOI":"10.1029\/96JC00798","article-title":"An Improved Algorithm for the Retrieval of Ocean Wave Spectra from Synthetic Aperture Radar Image Spectra","volume":"101","author":"Hasselmann","year":"1996","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_8","first-page":"C05004","article-title":"A Parametric Scheme for the Retrieval of Two-Dimensional Ocean Wave Spectra from Synthetic Aperture Radar Look Cross Spectra","volume":"110","author":"Lehner","year":"2005","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"6481","DOI":"10.1029\/JC086iC07p06481","article-title":"On the Detectability of Ocean Surface Waves by Real and Synthetic Aperture Radar","volume":"86","author":"Alpers","year":"1981","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"261","DOI":"10.1109\/36.992783","article-title":"Unconstrained Inversion of Waveheight Spectra from SAR Images","volume":"40","author":"Lyzenga","year":"2002","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_11","unstructured":"Bruck, M. (2015). Sea State Measurements Using TerraSAR-X\/TanDEM-X Data, Christian-Albrechts-Universit\u00e4t zu Kiel."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1109\/TGRS.2010.2052364","article-title":"Ocean Wave Integral Parameter Measurements Using ENVISAT ASAR Wave Mode Data","volume":"49","author":"Li","year":"2011","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"464","DOI":"10.1016\/j.isprsjprs.2016.02.001","article-title":"Meteo-Marine Parameters for Highly Variable Environment in Coastal Regions from Satellite Radar Images","volume":"119","author":"Pleskachevsky","year":"2016","journal-title":"ISPRS J. Photogr. Remote Sens."},{"key":"ref_14","first-page":"C03019","article-title":"An Empirical Approach for the Retrieval of Integral Ocean Wave Parameters from Synthetic Aperture Radar Data","volume":"112","author":"Lehner","year":"2007","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1827","DOI":"10.1002\/2016JC012364","article-title":"Significant wave heights from Sentinel-1 SAR: Validation and applications","volume":"122","author":"Stopa","year":"2017","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"999","DOI":"10.5194\/isprsarchives-XL-7-W3-999-2015","article-title":"Near Real Time Applications for Maritime Situational Awareness","volume":"40","author":"Schwarz","year":"2015","journal-title":"Int. Arch. Photogr. Remote Sens. Spat. Inf. Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"335","DOI":"10.5697\/oc.53-1-TI.335","article-title":"Spatial Patterns of the Wave Climate in the Baltic Proper and the Gulf of Finland","volume":"53","author":"Soomere","year":"2011","journal-title":"Oceanologia"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1016\/j.oceaneng.2018.01.048","article-title":"Comparing a 41-year model hindcast with decades of wave measurements from the Baltic Sea","volume":"152","author":"Lukas","year":"2018","journal-title":"Ocean Eng."},{"key":"ref_19","first-page":"451","article-title":"Wave hindcast statistics in the seasonally ice-covered Baltic sea","volume":"16","author":"Tuomi","year":"2011","journal-title":"Boreal Environ. Res."},{"key":"ref_20","unstructured":"Pleskachevsky, A., Jacobsen, S., Tings, B., and Schwarz, E. Sea State from Sentinel-1 Synthetic Aperture Radar Imagery for Maritime Situation Awareness. Int. J. Remote Sens., submitted."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1256","DOI":"10.1080\/01431161.2017.1399475","article-title":"Sea state in the Baltic Sea from space-borne high-resolution synthetic aperture radar imagery","volume":"39","author":"Rikka","year":"2018","journal-title":"Int. J. Remote Sens."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"3131","DOI":"10.1109\/JSTARS.2016.2539501","article-title":"Investigation into Different Polarimetric Features for Sea Ice Classification Using X-Band Synthetic Aperture Radar","volume":"9","author":"Ressel","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Singha, S., Velotto, D., and Lehner, S. (2015, January 26\u201331). Dual-polarimetric feature extraction and evaluation for oil spill detection: A near real time perspective. Proceedings of the 2015 IEEE International on Geoscience and Remote Sensing Symposium (IGARSS), Milan, Italy.","DOI":"10.1109\/IGARSS.2015.7326507"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"993","DOI":"10.1109\/JOE.2016.2520216","article-title":"First Comparison of Sentinel-1 and TerraSAR-X Data in the Framework of Maritime Targets Detection: South Italy Case","volume":"41","author":"Velotto","year":"2016","journal-title":"IEEE J. Ocean. Eng."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1016\/j.rse.2016.11.024","article-title":"Measuring ocean waves in sea ice using SAR imagery: A quasi-deterministic approach evaluated with Sentinel-1 and in situ data","volume":"189","author":"Ardhuin","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Shao, W., Zhang, Z., Li, X., and Li, H. (2016). Ocean wave parameters retrieval from Sentinel-1 SAR imagery. Remote Sens., 8.","DOI":"10.3390\/rs8090707"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Ardhuin, F., Chapron, B., and Collard, F. (2009). Observation of swell dissipation across oceans. Geophys. Res. Lett., 36.","DOI":"10.1029\/2008GL037030"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Collard, F., Ardhuin, F., and Chapron, B. (2009). Monitoring and analysis of ocean swell fields from space: New methods for routine observations. J. Geophys. Res. Oceans, 114.","DOI":"10.1029\/2008JC005215"},{"key":"ref_29","unstructured":"Tuomi, L., V\u00e4h\u00e4-Piikki\u00f6, O., and Alari, V. (2017). Baltic Sea Wave Analysis and Forecasting Product BALTICSEA_ANALYSIS_FORECAST_WAV_003_010, CMEMS."},{"key":"ref_30","unstructured":"Tuomi, L., V\u00e4h\u00e4-Piikki\u00f6, O., and Alari, V. (2017, January 3\u20135). CMEMS Baltic Monitoring and Forecasting Centre: High-resolution wave forecast in the seasonally ice-covered Baltic Sea. Proceedings of the 8th International EuroGOOS Conference, Bergen, Norway."},{"key":"ref_31","first-page":"s235","article-title":"The Copernicus marine environment monitoring service ocean state report","volume":"9","author":"Axell","year":"2016","journal-title":"J. Oper. Ocean."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1775","DOI":"10.1175\/1520-0485(1988)018<1775:TWMTGO>2.0.CO;2","article-title":"The WAM model\u2014A third generation ocean wave prediction model","volume":"18","author":"Group","year":"1988","journal-title":"J. Phys. Ocean."},{"key":"ref_33","unstructured":"Whitham, G.B. (1974). Linear and Nonlinear Waves, John Wiley & Sons."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"5767","DOI":"10.1029\/96JC02860","article-title":"Scatterometer data interpretation: Estimation and validation of the transfer function CMOD4","volume":"102","author":"Stoffelen","year":"1997","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Hersbach, H., Stoffelen, A., and de Haan, S. (2007). An improved C-band scatterometer ocean geophysical model function: CMOD5. J. Geophys. Res. Oceans, 112.","DOI":"10.1029\/2006JC003743"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"2638","DOI":"10.1109\/JSTARS.2015.2504324","article-title":"Preliminary evaluation of Sentinel-1A wind speed retrievals","volume":"9","author":"Monaldo","year":"2016","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Thompson, D.R., Elfouhaily, T.M., and Chapron, B. (1998, January 6\u201310). Polarization ratio for microwave backscattering from the ocean surface at low to moderate incidence angles. Proceedings of the 1998 IEEE International on Geoscience and Remote Sensing Symposium (IGARSSS\u201998), Seattle, WA, USA.","DOI":"10.1109\/IGARSS.1998.692411"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"2887","DOI":"10.1109\/TGRS.2014.2366433","article-title":"Tropical cyclone winds retrieved from C-band cross-polarized synthetic aperture radar","volume":"53","author":"Horstmann","year":"2015","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_39","unstructured":"Skamarock, W.C., Klemp, J.B., Dudhia, J., Gill, D.O., Barker, D.M., Wang, W., and Powers, J.G. (2005). A Description of the Advanced Research WRF Version 2 (No. NCAR\/TN-468+ STR), National Center For Atmospheric Research Boulder Co Mesoscale and Microscale Meteorology Div."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"610","DOI":"10.1109\/TSMC.1973.4309314","article-title":"Textural Features for Image Classification","volume":"3","author":"Haralick","year":"1973","journal-title":"IEEE Trans. Syst. Man Cyber."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"1320","DOI":"10.1109\/TGRS.2014.2337663","article-title":"A new approach to ocean wave parameter estimates from C-band ScanSAR images","volume":"53","author":"Romeiser","year":"2015","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Alari, V., Staneva, J., Breivik, \u00d8., Bidlot, J.-R., Mogensen, K., and Janssen, P. (2016, January 17\u201322). Response of water temperature to surface wave effects in the Baltic Sea: Simulations with the coupled NEMO-WAM model. Proceedings of the EGU General Assembly Conference Abstracts, Vienna Austria.","DOI":"10.1007\/s10236-016-0963-x"},{"key":"ref_43","unstructured":"European Maritime Safety Agency (2011). EMSA CleanSeaNet First Generation Report, EMSA."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"19477","DOI":"10.1029\/2000JC900063","article-title":"Global high-resolution mapping of ocean circulation from TOPEX\/Poseidon and ERS-1 and-2","volume":"105","author":"Ducet","year":"2000","journal-title":"J. Geophys. Res. Oceans"},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Pascual, A., Faug\u00e8re, Y., Larnicol, G., and Le Traon, P.Y. (2006). Improved description of the ocean mesoscale variability by combining four satellite altimeters. Geophys. Res. Lett., 33.","DOI":"10.1029\/2005GL024633"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"1067","DOI":"10.5194\/os-12-1067-2016","article-title":"DUACS DT2014: The new multi-mission altimeter data set reprocessed over 20 years","volume":"12","author":"Pujol","year":"2016","journal-title":"Ocean Sci."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1080\/714044527","article-title":"Simultaneous ocean wave measurements by the Jason and Topex satellites, with buoy and model comparisons special issue: Jason-1 calibration\/Validation","volume":"26","author":"Ray","year":"2003","journal-title":"Mar. Geod."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Bouffard, J., Vignudelli, S., Cipollini, P., and Menard, Y. (2008). Exploiting the potential of an improved multimission altimetric data set over the coastal ocean. Geophys. Res. Lett., 35.","DOI":"10.1029\/2008GL033488"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1016\/S0921-8181(02)00106-6","article-title":"Sea level variations in the Mediterranean Sea and Black Sea from satellite altimetry and tide gauges","volume":"34","author":"Cazenave","year":"2002","journal-title":"Glob. Plan. Chang."},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Kudryavtseva, N.A., and Soomere, T. (arXiv, 2016). Validation of the multi-mission altimeter wave height data for the Baltic Sea region, arXiv.","DOI":"10.3176\/earth.2016.13"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Madsen, K.S., H\u00f8yer, J., and Tscherning, C.C. (2007). Near-coastal satellite altimetry: Sea surface height variability in the North Sea\u2013Baltic Sea area. Geophys. Res. Lett., 34.","DOI":"10.1029\/2007GL029965"},{"key":"ref_52","doi-asserted-by":"crossref","unstructured":"Vignudelli, S., Cipollini, P., Roblou, L., Lyard, F., Gasparini, G., Manzella, G., and Astraldi, M. (2005). Improved satellite altimetry in coastal systems: Case study of the Corsica Channel (Mediterranean Sea). Geophys. Res. Lett., 32.","DOI":"10.1029\/2005GL022602"},{"key":"ref_53","unstructured":"H\u00f8yer, J.L., and Nielsen, J. (2006, January 13\u201318). Satellite significant wave height observations in coastal and shelf seas. Proceedings of the Symposium on 15 Years of Progress in Radar Altimetry, Venice, Italy."},{"key":"ref_54","doi-asserted-by":"crossref","unstructured":"Kudryavtseva, N., and Soomere, T. (arXiv, 2017). Satellite altimetry reveals spatial patterns of variations in the Baltic Sea wave climate, arXiv.","DOI":"10.5194\/esd-2016-68"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/5\/757\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:04:19Z","timestamp":1760195059000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/5\/757"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,5,15]]},"references-count":54,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2018,5]]}},"alternative-id":["rs10050757"],"URL":"https:\/\/doi.org\/10.3390\/rs10050757","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,5,15]]}}}