Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over West Africa

This study presents a comprehensive comparison of radar altimetry signatures at Ka-, Ku-, C-, and S-bands using SARAL, ENVISAT and Jason-2 data over the major bioclimatic zones, soil and vegetation types encountered in West-Africa, with an emphasis on the new information at Ka-band provided by the recently launched SARAL–Altika mission. Spatio-temporal variations of the radar altimetry responses were related to changes in surface roughness, land cover and soil wetness. Analysis of time series of backscattering coefficients along the West African bioclimatic gradient shows that radar echoes at nadir incidence are well correlated to soil moisture in semi-arid savannah environments. Radar altimeters are able to detect the presence of water even under a dense canopy cover at all frequencies. But only measurements at Ka-band are able to penetrate underneath the canopy of non-inundated tropical evergreen forests.

[1]  Harold C. Macdonald,et al.  "Vegetation Penetration" with K-Band Imaging Radars , 1971 .

[2]  Nick van de Giesen,et al.  Characterization of west African shallow flood plains with L- and C-band radar , 2001 .

[3]  Klaus Scipal,et al.  An Improved Soil Moisture Retrieval Algorithm for ERS and METOP Scatterometer Observations , 2009, IEEE Transactions on Geoscience and Remote Sensing.

[4]  Frédéric Baup,et al.  The AMMA-CATCH Gourma observatory site in Mali: Relating climatic variations to changes in vegetation, surface hydrology, fluxes and natural resources , 2009 .

[5]  C. Prigent,et al.  Surface freshwater storage and dynamics in the Amazon basin during the 2005 exceptional drought , 2012 .

[6]  Dominique Tapsoba,et al.  Rainfall Variability in West Africa during the Years 1950-90 , 2002 .

[7]  Y. Kerr,et al.  L-band Microwave Emission of the Biosphere (L-MEB) Model: Description and calibration against experimental data sets over crop fields , 2007 .

[8]  David G. Long,et al.  Discrimination of Africa's vegetation using reconstructed ERS-1 imagery , 1996, IGARSS '96. 1996 International Geoscience and Remote Sensing Symposium.

[9]  G. Huffman,et al.  The TRMM Multi-Satellite Precipitation Analysis (TMPA) , 2010 .

[10]  Marc Simard,et al.  Mapping tropical coastal vegetation using JERS-1 and ERS-1 radar data with a decision tree classifier , 2002 .

[11]  Filipe Aires,et al.  Multiangle Backscattering Observations of Continental Surfaces in Ku-Band (13 GHz) From Satellites: Understanding the Signals, Particularly in Arid Regions , 2015, IEEE Transactions on Geoscience and Remote Sensing.

[12]  Pierre Borderies,et al.  Spaceborne altimetry and scatterometry backscattering signatures at C- and Ku-bands over West Africa , 2015 .

[13]  Richard K. Moore,et al.  Microwave Remote Sensing, Active and Passive , 1982 .

[14]  C. Birkett,et al.  Evaluation of JERS-1 SAR mosaics for hydrological applications in the Congo river basin , 2002 .

[15]  R. Jeu,et al.  Multisensor historical climatology of satellite‐derived global land surface moisture , 2008 .

[16]  Javier Tomasella,et al.  Satellite-based estimates of groundwater storage variations in large drainage basins with extensive floodplains , 2011 .

[17]  Frédéric Baup,et al.  Mapping surface soil moisture over the Gourma mesoscale site (Mali) by using ENVISAT ASAR data , 2010 .

[18]  Mehrez Zribi,et al.  Soil moisture mapping based on ASAR/ENVISAT radar data over a Sahelian region , 2007 .

[19]  A. Cazenave,et al.  Preliminary results of ENVISAT RA-2-derived water levels validation over the Amazon basin , 2006 .

[20]  Y. Hong,et al.  The TRMM Multisatellite Precipitation Analysis (TMPA): Quasi-Global, Multiyear, Combined-Sensor Precipitation Estimates at Fine Scales , 2007 .

[21]  David Griffin,et al.  The SARAL/AltiKa Altimetry Satellite Mission , 2015 .

[22]  Pierre-Louis Frison,et al.  Use of ERS-1 wind scatterometer data over land surfaces , 1996, IEEE Trans. Geosci. Remote. Sens..

[23]  Arnaud Mialon,et al.  The SMOS Soil Moisture Retrieval Algorithm , 2012, IEEE Transactions on Geoscience and Remote Sensing.

[24]  Frédéric Frappart,et al.  Preliminary Assessment of SARAL/AltiKa Observations over the Ganges-Brahmaputra and Irrawaddy Rivers , 2015 .

[25]  D. Fernández-Prieto,et al.  Monitoring and assessment of wetlands using Earth Observation: the GlobWetland project. , 2009, Journal of environmental management.

[26]  Frédérique Seyler,et al.  Water level dynamics of Amazon wetlands at the watershed scale by satellite altimetry , 2012 .

[27]  Frédéric Baup,et al.  ERS scatterometer surface soil moisture analysis of two sites in the south and north of the Sahel region of West Africa. , 2009 .

[28]  Kalifa Goita,et al.  Radar altimetry of water level variability in the Inner Delta of Niger River , 2012, 2012 IEEE International Geoscience and Remote Sensing Symposium.

[29]  Maurice Borgeaud,et al.  A study of vegetation cover effects on ERS scatterometer data , 1999, IEEE Trans. Geosci. Remote. Sens..

[30]  C. Prigent,et al.  Interannual variations of river water storage from a multiple satellite approach: A case study for the Rio Negro River basin , 2008 .

[31]  C. Birkett,et al.  Contribution of the TOPEX NASA Radar Altimeter to the global monitoring of large rivers and wetlands , 1998 .

[32]  C. Birkett,et al.  The contribution of TOPEX/POSEIDON to the global monitoring of climatically sensitive lakes , 1995 .

[33]  D. Kuijper,et al.  Analysis of Envisat Orbit Maintenance Strategies to Improve/Increase Envisat ASAR Interferometry Opportunities , 2007 .

[34]  S. Calmant,et al.  Water levels in the Amazon basin derived from the ERS 2 and ENVISAT radar altimetry missions , 2010 .

[35]  Philippa A. M. Berry,et al.  Soil Surface Moisture From EnviSat RA-2: From Modelling Towards Implementation , 2010 .

[36]  Laurent Rey,et al.  AltiKa: a Ka-band Altimetry Payload and System for Operational Altimetry during the GMES Period , 2006, Sensors (Basel, Switzerland).

[37]  K. Sarabandi,et al.  Millimeter-wave measurements of foliage attenuation and ground reflectivity of tree stands at nadir incidence , 2004, IEEE Transactions on Antennas and Propagation.

[38]  W. Wagner,et al.  A Method for Estimating Soil Moisture from ERS Scatterometer and Soil Data , 1999 .

[39]  Frédéric Frappart,et al.  WATER VOLUME CHANGE IN THE LOWER MEKONG FROM SATELLITE ALTIMETRY AND IMAGERY DATA , 2006 .

[40]  Jeff Ridley,et al.  Radar backscatter characteristics of a desert surface , 1996 .

[41]  Sharon E. Nicholson,et al.  Rainfall and Atmospheric Circulation during Drought Periods and Wetter Years in West Africa , 1981 .

[42]  Dirk H. Hoekman,et al.  Determining land-surface parameters from the ERS wind scatterometer , 2000, IEEE Trans. Geosci. Remote. Sens..

[43]  H. Isnard.  Esquisse du climat de la Libye , 1968 .

[44]  Nicolas Baghdadi,et al.  Mapping of Central Africa Forested Wetlands Using Remote Sensing , 2014, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing.

[45]  Duncan J. Wingham,et al.  NEW TECHNIQUES IN SATELLITE ALTIMETER TRACKING SYSTEMS. , 1986 .

[46]  A. Cazenave,et al.  Floodplain water storage in the Negro River basin estimated from microwave remote sensing of inundation area and water levels , 2005 .

[47]  S. Nicholson.  The Nature of Rainfall Fluctuations in Subtropical West Africa , 1980 .

[48]  Alenia Aerospazio,et al.  ENVISAT RA-2 ADVANCED RADAR ALTIMETER : INSTRUMENT DESIGN AND PRE-LAUNCH PERFORMANCE ASSESSMENT REVIEW , 1999 .

[49]  David G. Long,et al.  Spatial and Temporal Behavior of Microwave Backscatter Directional Modulation Over the Saharan Ergs , 2007, IEEE Transactions on Geoscience and Remote Sensing.

[50]  Fabrice Papa,et al.  Use of the Topex-Poseidon dual-frequency radar altimeter over land surfaces , 2003 .

[51]  Pierre Hiernaux,et al.  Observations and Interpretation of Seasonal ERS-1 Wind Scatterometer Data over Northern Sahel (Mali) , 1998 .

[52]  A. Lopes,et al.  Preliminary analysis of ERS-1 wind scatterometer data over land surfaces , 1995 .

[53]  Eric Mougin,et al.  Monitoring global vegetation dynamics with ERS-1 wind scatterometer data , 1996 .

[54]  P. Rosnay,et al.  Surface soil moisture estimation over the AMMA Sahelian site in Mali using ENVISAT/ASAR data , 2007 .

[55]  Marc Simard,et al.  Large-scale vegetation maps derived from the combined L-band GRFM and C-band CAMP wide area radar mosaics of Central Africa , 2002 .

[56]  F. Ulaby,et al.  Microwave Dielectric Behavior of Wet Soil-Part 1: Empirical Models and Experimental Observations , 1985, IEEE Transactions on Geoscience and Remote Sensing.

[57]  M. Owe.  Remote Sensing and Hydrology 2000 , 2001 .

[58]  Frédéric Frappart,et al.  Estimating surface soil moisture over Sahel using ENVISAT radar altimetry , 2012 .

[59]  A. Cazenave,et al.  SOLS: A lake database to monitor in the Near Real Time water level and storage variations from remote sensing data , 2011 .

[60]  David G. Long,et al.  Microwave backscatter modeling of erg surfaces in the Sahara desert , 2005, IEEE Transactions on Geoscience and Remote Sensing.