{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,26]],"date-time":"2026-03-26T15:37:05Z","timestamp":1774539425425,"version":"3.50.1"},"reference-count":55,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2018,11,22]],"date-time":"2018-11-22T00:00:00Z","timestamp":1542844800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000844","name":"European Space Agency","doi-asserted-by":"publisher","award":["4000113119\/15\/I-SB0"],"award-info":[{"award-number":["4000113119\/15\/I-SB0"]}],"id":[{"id":"10.13039\/501100000844","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Microwave Emission Models (EM) are used in retrieval algorithms to estimate geophysical state parameters such as soil Water Content (    W C    ) and vegetation optical depth (   \u03c4   ), from brightness temperatures      T B  p , \u03b8       measured at nadir angles    \u03b8    at Horizontal and Vertical polarizations     p =  {  H , V  }     . An EM adequate for implementation in a retrieval algorithm must capture the responses of      T B  p , \u03b8       to the retrieval parameters, and the EM parameters must be experimentally accessible and representative of the measurement footprint. The objective of this study is to explore the benefits of the multiple-scattering Two-Stream (2S) EM over the \u201cTau-Omega\u201d (TO) EM considered as the \u201creference\u201d to retrieve     W C     and    \u03c4    from L-band      T B  p , \u03b8      . For sparse and low-scattering vegetation      T  B , E M   p , \u03b8       simulated with     E M =  {  TO , \u00a0 2 S  }      converge. This is not the case for dense and strongly scattering vegetation. Two-Parameter (2P) retrievals     2   P   R C   =  (  W  C  R C   ,  \u03c4  R C    )      are computed from elevation scans      T B  p ,  \u03b8 j    =  T  B , TO   p ,  \u03b8 j        synthesized with TO EM and from      T B  p ,  \u03b8 j        measured from a tower within a deciduous forest. Retrieval Configurations (    R C    ) employ either     E M = TO     or     E M = 2 S     and assume fixed scattering albedos.     W  C  R C       achieved with the 2S RC is marginally lower (    ~ 1    \u00a0 m   3   m  \u2212 3      ) than if achieved with the \u201creference\u201d TO RC, while      \u03c4  R C       is reduced considerably when using 2S EM instead of TO EM. Our study outlines a number of advantages of the 2S EM over the TO EM currently implemented in the operational SMOS and SMAP retrieval algorithms.<\/jats:p>","DOI":"10.3390\/rs10121868","type":"journal-article","created":{"date-parts":[[2018,11,23]],"date-time":"2018-11-23T03:41:31Z","timestamp":1542944491000},"page":"1868","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":53,"title":["\u201cTau-Omega\u201d- and Two-Stream Emission Models Used for Passive L-Band Retrievals: Application to Close-Range Measurements over a Forest"],"prefix":"10.3390","volume":"10","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1569-1564","authenticated-orcid":false,"given":"Mike","family":"Schwank","sequence":"first","affiliation":[{"name":"Swiss Federal Research Institute WSL, CH-8903 Birmensdorf, Switzerland"},{"name":"Gamma Remote Sensing AG, CH-3073 G\u00fcmligen, Switzerland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2601-5123","authenticated-orcid":false,"given":"Reza","family":"Naderpour","sequence":"additional","affiliation":[{"name":"Swiss Federal Research Institute WSL, CH-8903 Birmensdorf, Switzerland"}]},{"given":"Christian","family":"M\u00e4tzler","sequence":"additional","affiliation":[{"name":"Gamma Remote Sensing AG, CH-3073 G\u00fcmligen, Switzerland"}]}],"member":"1968","published-online":{"date-parts":[[2018,11,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1560","DOI":"10.1126\/science.1082750","article-title":"Climate-driven increases in global terrestrial net primary production from 1982 to 1999","volume":"300","author":"Nemani","year":"2003","journal-title":"Science"},{"key":"ref_2","unstructured":"Anderson, M.G., and Burt, T. (1985). Remote sensing of soil moisture. Encyclopedia of Hydrological Forecasting, John Wiley & Sons."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1109\/TGRS.1982.4307514","article-title":"Microwave radiometry of lands under natural and artificial moistening","volume":"GE-20","author":"Shutko","year":"1982","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"M\u00e4tzler, C. (2006). Thermal Microwave Radiation: Applications for Remote Sensing, Institution of Engineering and Technology.","DOI":"10.1049\/PBEW052E"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"433","DOI":"10.1109\/36.485121","article-title":"Passive microwave remote sensing of forests: A model investigation","volume":"34","author":"Ferrazzoli","year":"1996","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"2700","DOI":"10.1109\/TGRS.2002.807577","article-title":"Simulating L-band emission of forests in view of future satellite applications","volume":"40","author":"Ferrazzoli","year":"2002","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Guglielmetti, M., Schwank, M., M\u00e4tzler, C., Oberd\u00f6rster, C., Vanderborght, J., and Fl\u00fchler, H. (2007). Measured microwave radiative transfer properties of a deciduous forest canopy. Remote Sens. Environ., 523\u2013532.","DOI":"10.1016\/j.rse.2007.02.003"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"727","DOI":"10.1109\/TGRS.2007.914797","article-title":"Fosmex: Forest soil moisture experiments with microwave radiometry","volume":"46","author":"Guglielmetti","year":"2008","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"51","DOI":"10.1109\/TGRS.1983.350530","article-title":"Effects of vegetation cover on the microwave radiometric sensitivity to soil moisture","volume":"GE-21","author":"Ulaby","year":"1983","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1016\/j.rse.2015.10.021","article-title":"Comparison of SMOS and AMSR-E vegetation optical depth to four MODIS-based vegetation indices","volume":"172","author":"Grant","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"786","DOI":"10.1109\/TGRS.2003.821889","article-title":"The B-factor as a function of frequency and canopy type at H-polarization","volume":"42","author":"Wigneron","year":"2004","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1729","DOI":"10.1109\/36.942551","article-title":"Soil moisture retrieval from space: The soil moisture and ocean salinity (SMOS) mission","volume":"39","author":"Kerr","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"68","DOI":"10.5670\/oceanog.2008.68","article-title":"The AQUARIUS\/SAC-D mission designed to meet the salinity remote-sensing challenge","volume":"21","author":"Lagerloef","year":"2008","journal-title":"Oceanography"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"688","DOI":"10.1109\/JPROC.2010.2040550","article-title":"Aquarius and remote sensing of sea surface salinity from space","volume":"98","author":"Vine","year":"2010","journal-title":"Proc. IEEE"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"923","DOI":"10.1109\/LGRS.2014.2364151","article-title":"Global soil moisture from the aquarius\/sac-d satellite: Description and initial assessment","volume":"12","author":"Bindlish","year":"2015","journal-title":"IEEE Geosci Remote Sens."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"666","DOI":"10.1109\/JPROC.2010.2043032","article-title":"The SMOS mission: New tool for monitoring key elements of the global water cycle","volume":"98","author":"Kerr","year":"2010","journal-title":"Proc. IEEE"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"704","DOI":"10.1109\/JPROC.2010.2043918","article-title":"The Soil Moisture Active Passive (SMAP) Mission","volume":"98","author":"Entekhabi","year":"2010","journal-title":"Proc. IEEE"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"594","DOI":"10.1109\/TGRS.2007.914809","article-title":"SMOS: The payload","volume":"46","author":"McMullan","year":"2008","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"377","DOI":"10.1016\/j.rse.2016.02.002","article-title":"Snow density and ground permittivity retrieved from L-band radiometry: Application to experimental data","volume":"180","author":"Lemmetyinen","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Naderpour, R., and Schwank, M. (2018). Snow wetness retrieved from L-band radiometry. Remote Sens., 10.","DOI":"10.3390\/rs10030359"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Naderpour, R., Schwank, M., and M\u00e4tzler, C. (2017). Davos-laret remote sensing field laboratory: 2016\/2017 winter season L-band measurements data-processing and analysis. Remote Sens., 9.","DOI":"10.3390\/rs9111185"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"3148","DOI":"10.1109\/JSTARS.2017.2669336","article-title":"Snow density and ground permittivity retrieved from L-band radiometry: A retrieval sensitivity analysis","volume":"10","author":"Naderpour","year":"2017","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3833","DOI":"10.1109\/JSTARS.2015.2422998","article-title":"Snow density and ground permittivity retrieved from L-band radiometry: A synthetic analysis","volume":"8","author":"Schwank","year":"2015","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Schwank, M., and Naderpour, R. (2018). Snow density and ground permittivity retrieved from L-band radiometry: Melting effects. Remote Sens., 10.","DOI":"10.3390\/rs10020354"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1016\/j.rse.2017.03.007","article-title":"Retrieving landscape freeze\/thaw state from soil moisture active passive (SMAP) radar and radiometer measurements","volume":"194","author":"Derksen","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Kim, S., Zyl, J.V., McDonald, K., and Njoku, E. (2010, January 10\u201314). Monitoring surface soil moisture and freeze-thaw state with the high-resolution radar of the soil moisture active\/passive (SMAP) mission. Proceedings of the 2010 IEEE Radar Conference, Washington, DC, USA.","DOI":"10.1109\/RADAR.2010.5494523"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1483","DOI":"10.1109\/TGRS.2011.2167755","article-title":"L-band radiometer observations of soil processes in boreal and subarctic environments","volume":"50","author":"Rautiainen","year":"2012","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"206","DOI":"10.1016\/j.rse.2014.03.007","article-title":"Detection of soil freezing from L-band passive microwave observations","volume":"147","author":"Rautiainen","year":"2014","journal-title":"Remote Sens. Environ."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Fernandez-Moran, R., Al-Yaari, A., Mialon, A., Mahmoodi, A., Al Bitar, A., De Lannoy, G., Rodriguez-Fernandez, N., Lopez-Baeza, E., Kerr, Y., and Wigneron, J.-P. (2017). SMOS-IC: An alternative smos soil moisture and vegetation optical depth product. Remote Sens., 9.","DOI":"10.20944\/preprints201703.0145.v1"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"460","DOI":"10.1016\/j.rse.2017.06.037","article-title":"L-band vegetation optical depth and effective scattering albedo estimation from smap","volume":"198","author":"Konings","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"178","DOI":"10.1016\/j.rse.2015.11.009","article-title":"Vegetation optical depth and scattering albedo retrieval using time series of dual-polarized L-band radiometer observations","volume":"172","author":"Konings","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1016\/j.rse.2016.03.004","article-title":"Smos retrieval over forests: Exploitation of optical depth and tests of soil moisture estimates","volume":"180","author":"Vittucci","year":"2016","journal-title":"Remote Sens. Environ."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"11229","DOI":"10.1029\/JC087iC13p11229","article-title":"A model for microwave emission from vegetation-covered fields","volume":"87","author":"Mo","year":"1982","journal-title":"J. Geophys. Res."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1430","DOI":"10.1109\/JSTARS.2013.2256339","article-title":"SMOS level 2 retrieval algorithm over forests: Description and generation of global maps","volume":"6","author":"Rahmoune","year":"2013","journal-title":"IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens."},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"M\u00e4tzler, C. (2000). Radiative Transfer Models for Microwave Radiometry: Final Report; Cost Action 712: Application of Microwave Radiometry to Atmospheric Research and Monitoring-Project 1: Development of Radiative Transfer Models, Office for Office Publication of the European Communities.","DOI":"10.1049\/PBEW052E_ch1"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"238","DOI":"10.1016\/j.rse.2017.01.024","article-title":"Modelling the passive microwave signature from land surfaces: A review of recent results and application to the L-band SMOS & SMAP soil moisture retrieval algorithms","volume":"192","author":"Wigneron","year":"2017","journal-title":"Remote Sens. Environ."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"324","DOI":"10.1016\/j.rse.2018.10.022","article-title":"Characterization of higher-order scattering from vegetation with smap measurements","volume":"219","author":"Feldman","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"508","DOI":"10.1109\/LGRS.2007.900687","article-title":"Modeling forest emissivity at L-band and a comparison with multitemporal measurements","volume":"4","author":"Ferrazzoli","year":"2007","journal-title":"IEEE Trans. Geosci. Remote Sens. Lett."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"364","DOI":"10.1109\/LGRS.2006.873230","article-title":"Simulating L-band emission of coniferous forests using a discrete model and a detailed geometrical representation","volume":"3","author":"Saleh","year":"2006","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"6111","DOI":"10.1063\/1.367496","article-title":"Improved born approximation for scattering of radiation in a granular medium","volume":"83","year":"1998","journal-title":"J. Appl. Phys."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1016\/S0034-4257(99)00046-2","article-title":"Microwave emission model of layered snowpacks","volume":"70","author":"Wiesmann","year":"1999","journal-title":"Remote Sens. Environ."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Roy, A., Leduc-Leballeur, M., Picard, G., Royer, A., Toose, P., Derksen, C., Lemmetyinen, J., Berg, A., Rowlandson, T., and Schwank, M. (2018). Modelling the L-band snow-covered surface emission in a winter canadian prairie environment. Remote Sens., 10.","DOI":"10.3390\/rs10091451"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"180","DOI":"10.1016\/j.rse.2014.08.029","article-title":"Model for microwave emission of a snow-covered ground with focus on L band","volume":"154","author":"Schwank","year":"2014","journal-title":"Remote Sens. Environ."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"2001","DOI":"10.1109\/TGRS.2015.2493505","article-title":"Differences between the hut snow emission model and memls and their effects on brightness temperature simulation","volume":"54","author":"Pan","year":"2016","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1378","DOI":"10.1109\/36.763302","article-title":"Hut snow emission model and its applicability to snow water equivalent retrieval","volume":"37","author":"Pulliainen","year":"1999","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"2024","DOI":"10.1109\/TGRS.2008.2010252","article-title":"Observations and modeling of a pine forest floor at L-band","volume":"47","author":"Grant","year":"2009","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"639","DOI":"10.1016\/j.rse.2006.10.014","article-title":"L-band microwave emission of the biosphere (L-MEB) model: Description and calibration against experimental data sets over crop fields","volume":"107","author":"Wigneron","year":"2007","journal-title":"Remote Sens. Environ."},{"key":"ref_48","unstructured":"Kerr, Y., Waldteufel, P., Richaume, P., Ferrazzoli, P., and Wigneron, J. (SMOS Level 2 Processor for Soil Mois, 2011). Algorithm theoretical basis document (ATBD) for the SMOS level 2 soil moisture processor development continuation project, SMOS Level 2 Processor for Soil Mois."},{"key":"ref_49","unstructured":"O\u2019Neill, P., Chan, S., Njoku, E., Jackson, T., and Bindlish, R. (2014). Algorithm Theoretical Basis Document Level 2 & 3 Soil Moisture (Passive) Data Products, JPL D-66480, Jet Propul, Laboratories of the California Institute of Technology."},{"key":"ref_50","first-page":"781","article-title":"Temperature dependable microwave dielectric model for a pine litter thawed and frozen","volume":"7","author":"Mironov","year":"2011","journal-title":"PIERS Online"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"1697","DOI":"10.1109\/36.942548","article-title":"A simple parameterization of the L-band microwave emission from rough agricultural soils","volume":"39","author":"Wigneron","year":"2001","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"2135","DOI":"10.1109\/TGRS.2003.815417","article-title":"Two-year global simulation of L-band brightness temperatures over land","volume":"41","author":"Pellarin","year":"2003","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_53","unstructured":"M\u00e4tzler, C., Weber, D., W\u00fcthrich, M., Schneeberger, K., Stamm, C., Wydler, H., and Fl\u00fchler, H. (2003). Elbara, the Eth L-band Radiometer for Soil-Moisture Research, Proceedings of the International Geoscience and Remote Sensing Symposium (IGARSS), Toulouse, France, 21\u201325 July 2003, IEEE."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"584","DOI":"10.3390\/s100100584","article-title":"Elbara II, an L-band radiometer system for soil moisture research","volume":"10","author":"Schwank","year":"2010","journal-title":"Sensors"},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"1982","DOI":"10.1109\/TGRS.2008.916983","article-title":"Testing a new model for the L-band radiation of moist leaf litter","volume":"46","author":"Schwank","year":"2008","journal-title":"IEEE Trans. Geosci. Remote Sens."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/12\/1868\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:31:30Z","timestamp":1760196690000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/10\/12\/1868"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,11,22]]},"references-count":55,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2018,12]]}},"alternative-id":["rs10121868"],"URL":"https:\/\/doi.org\/10.3390\/rs10121868","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,11,22]]}}}