Evaluation of soil moisture downscaling using a simple thermal-based proxy – the REMEDHUS network (Spain) example

Soil moisture retrieved from satellite microwave remote sensing normally has spatial resolution on the order of tens of kilometers, which are too coarse for many regional hydrological applications such as agriculture monitoring and drought prediction. Therefore, various downscaling methods have been proposed to enhance the spatial resolution of satellite soil moisture products. The aim of this study is to investigate the validity and robustness of the simple vegetation temperature condition index (VTCI) downscaling scheme over a dense soil moisture observational network (REMEDHUS) in Spain. First, the optimized VTCI was determined through sensitivity analyses of VTCI to surface temperature, vegetation index, cloud, topography, and land cover heterogeneity, using data from Moderate Resolution Imaging Spectroradiometer~(MODIS) and MSG SEVIRI (METEOSAT Second Generation – Spinning Enhanced Visible and Infrared Imager). Then the downscaling scheme was applied to improve the spatial resolution of the European Space Agency's Water Cycle Multi-mission Observation Strategy and Climate Change Initiative (ESA CCI) soil moisture, which is a merged product based on both active and passive microwave observations. The results from direct validation against soil moisture observations, spatial pattern comparison, as well as seasonal and land use analyses show that the downscaling method can significantly improve the spatial details of CCI soil moisture while maintaining the accuracy of CCI soil moisture. The accuracy level is comparable to other downscaling methods that were also validated against the REMEDHUS network. Furthermore, slightly better performance of MSG SEVIRI over MODIS was observed, which suggests the high potential of applying a geostationary satellite for downscaling soil moisture in the future. Overall, considering the simplicity, limited data requirements and comparable accuracy level to other complex methods, the VTCI downscaling method can facilitate relevant hydrological applications that require high spatial and temporal resolution soil moisture.

[1]  Wade T. Crow,et al.  An intercomparison of available soil moisture estimates from thermal infrared and passive microwave remote sensing and land surface modeling , 2011 .

[2]  Jie Wang,et al.  Spatial Downscaling of Satellite Soil Moisture Data Using a Vegetation Temperature Condition Index , 2016, IEEE Transactions on Geoscience and Remote Sensing.

[3]  Thomas J. Jackson,et al.  Soil moisture retrieval from AMSR-E , 2003, IEEE Trans. Geosci. Remote. Sens..

[4]  Terri S. Hogue,et al.  Improving Spatial Soil Moisture Representation Through Integration of AMSR-E and MODIS Products , 2012, IEEE Transactions on Geoscience and Remote Sensing.

[5]  George P. Petropoulos,et al.  Surface soil moisture retrievals from remote sensing: Current status, products & future trends , 2015 .

[6]  Klaus Scipal,et al.  Validation of ERS scatterometer‐derived soil moisture data in the central part of the Duero Basin, Spain , 2005 .

[7]  J. Sobrino,et al.  A method to estimate soil moisture from Airborne Hyperspectral Scanner (AHS) and ASTER data: Application to SEN2FLEX and SEN3EXP campaigns , 2012 .

[8]  Dawei Han,et al.  Machine Learning Techniques for Downscaling SMOS Satellite Soil Moisture Using MODIS Land Surface Temperature for Hydrological Application , 2013, Water Resources Management.

[9]  Wouter Dorigo,et al.  A Preliminary Study toward Consistent Soil Moisture from AMSR2 , 2015 .

[10]  C. Woodcock,et al.  Multiscale analysis and validation of the MODIS LAI product: I. Uncertainty assessment , 2002 .

[11]  A. Loew.  Impact of surface heterogeneity on surface soil moisture retrievals from passive microwave data at the regional scale: The Upper Danube case , 2008 .

[12]  B. Fang,et al.  Soil moisture at watershed scale: Remote sensing techniques , 2014 .

[13]  Wade T. Crow,et al.  Performance Metrics for Soil Moisture Retrievals and Application Requirements , 2009 .

[14]  Arnaud Mialon,et al.  SMOS CATDS level 3 global products over land , 2010, Remote Sensing.

[15]  V. K. Dadhwal,et al.  Assessing potential of MODIS derived temperature/vegetation condition index (TVDI) to infer soil moisture status , 2009 .

[16]  Minha Choi,et al.  A microwave-optical/infrared disaggregation for improving spatial representation of soil moisture using AMSR-E and MODIS products , 2012 .

[17]  Alexander Loew,et al.  Evaluation of Daytime Evaporative Fraction from MODIS TOA Radiances Using FLUXNET Observations , 2014, Remote. Sens..

[18]  Klaus Scipal,et al.  Temporal Stability of Soil Moisture and Radar Backscatter Observed by the Advanced Synthetic Aperture Radar (ASAR) , 2008, Sensors.

[19]  José Martínez-Fernández,et al.  Validation of the SMOS L2 Soil Moisture Data in the REMEDHUS Network (Spain) , 2012, IEEE Transactions on Geoscience and Remote Sensing.

[20]  C. DaCamara,et al.  Land surface temperature and emissivity estimation based on the two-temperature method: sensitivity analysis using simulated MSG/SEVIRI data , 2004 .

[21]  Jean-François Mahfouf,et al.  Evaluation of the Optimum Interpolation and Nudging Techniques for Soil Moisture Analysis Using FIFE Data , 2000 .

[22]  Wei Zhao,et al.  Surface Soil Water Content Estimation from Thermal Remote Sensing based on the Temporal Variation of Land Surface Temperature , 2014, Remote. Sens..

[23]  András Bárdossy,et al.  Spatial distribution of soil moisture in a small catchment. Part 1: geostatistical analysis , 1998 .

[24]  G. Petropoulos,et al.  A review of Ts/VI remote sensing based methods for the retrieval of land surface energy fluxes and soil surface moisture , 2009 .

[25]  Inge Sandholt,et al.  Estimation of regional evapotranspiration over the North China Plain using geostationary satellite data , 2011, Int. J. Appl. Earth Obs. Geoinformation.

[26]  R. Fensholt,et al.  Evaluation of MODIS LAI, fAPAR and the relation between fAPAR and NDVI in a semi-arid environment using in situ measurements , 2004 .

[27]  N. Lu,et al.  Spatial upscaling of in-situ soil moisture measurements based on MODIS-derived apparent thermal inertia , 2013 .

[28]  Ralf Ludwig,et al.  Derivation of surface soil moisture from ENVISAT ASAR wide swath and image mode data in agricultural areas , 2006, IEEE Transactions on Geoscience and Remote Sensing.

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

[30]  Yann Kerr,et al.  Soil moisture retrieval from space: the Soil Moisture and Ocean Salinity (SMOS) mission , 2001, IEEE Trans. Geosci. Remote. Sens..

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

[32]  I. Sandholt,et al.  A simple interpretation of the surface temperature/vegetation index space for assessment of surface moisture status , 2002 .

[33]  Z. Wan,et al.  Using MODIS Land Surface Temperature and Normalized Difference Vegetation Index products for monitoring drought in the southern Great Plains, USA , 2004 .

[34]  S. Sánchez-Ruiz,et al.  Combining SMOS with visible and near/shortwave/thermal infrared satellite data for high resolution soil moisture estimates , 2014 .

[35]  Markus Reichstein,et al.  Modeling temporal and large‐scale spatial variability of soil respiration from soil water availability, temperature and vegetation productivity indices , 2003 .

[36]  Yi Y. Liu,et al.  Trend-preserving blending of passive and active microwave soil moisture retrievals , 2012 .

[37]  Yi Y. Liu,et al.  Developing an improved soil moisture dataset by blending passive and active microwave satellite-based retrievals , 2011 .

[38]  Jan Vanderborght,et al.  On the spatio-temporal dynamics of soil moisture at the field scale , 2014 .

[39]  W. Wagner,et al.  Skill and Global Trend Analysis of Soil Moisture from Reanalyses and Microwave Remote Sensing , 2013 .

[40]  A. Huete,et al.  Overview of the radiometric and biophysical performance of the MODIS vegetation indices , 2002 .

[41]  Adriano Camps,et al.  A Downscaling Approach for SMOS Land Observations: Evaluation of High-Resolution Soil Moisture Maps Over the Iberian Peninsula , 2014, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing.

[42]  Wenjiang Huang,et al.  A method of estimating soil moisture based on the linear decomposition of mixture pixels , 2013, Math. Comput. Model..

[43]  W. Verstraeten,et al.  Soil moisture retrieval using thermal inertia, determined with visible and thermal spaceborne data, validated for European forests , 2006 .

[44]  Rasmus Fensholt,et al.  Combining the triangle method with thermal inertia to estimate regional evapotranspiration — Applied to MSG-SEVIRI data in the Senegal River basin , 2008 .

[45]  Ahmad Al Bitar,et al.  A sequential model for disaggregating near-surface soil moisture observations using multi-resolution thermal sensors , 2009 .

[46]  T. Carlson,et al.  A method to make use of thermal infrared temperature and NDVI measurements to infer surface soil water content and fractional vegetation cover , 1994 .

[47]  Inge Sandholt,et al.  Validation and scale dependencies of the triangle method for the evaporative fraction estimation over heterogeneous areas , 2014 .

[48]  S. Seneviratne,et al.  Investigating soil moisture-climate interactions in a changing climate: A review , 2010 .

[49]  Kaniska Mallick,et al.  Estimating volumetric surface moisture content for cropped soils using a soil wetness index based on surface temperature and NDVI , 2009 .

[50]  Rasmus Fensholt,et al.  Comparisons of compositing period length for vegetation index data from polar-orbiting and geostationary satellites for the cloud-prone region of West Africa , 2007 .

[51]  W. Wagner,et al.  Fusion of active and passive microwave observations to create an Essential Climate Variable data record on soil moisture , 2012 .

[52]  D. Lobell,et al.  Moisture effects on soil reflectance , 2002 .

[53]  W. Wagner,et al.  Evaluation of the ESA CCI soil moisture product using ground-based observations , 2015 .

[54]  S. Miller,et al.  Spaceborne soil moisture estimation at high resolution: a microwave-optical/IR synergistic approach , 2003 .

[55]  Bo-Hui Tang,et al.  An application of the Ts–VI triangle method with enhanced edges determination for evapotranspiration estimation from MODIS data in arid and semi-arid regions: Implementation and validation , 2010 .

[56]  Yi Y. Liu,et al.  Evaluating global trends (1988–2010) in harmonized multi‐satellite surface soil moisture , 2012 .

[57]  Bojie Fu,et al.  Spatial variability of soil moisture content and its relation to environmental indices in a semi-arid gully catchment of the Loess Plateau, China , 2001 .

[58]  Yuanbo Liu,et al.  Uncertainties in Estimating Normalized Difference Temperature Index From TOA Radiances , 2013, IEEE Transactions on Geoscience and Remote Sensing.

[59]  Martha C. Anderson,et al.  An intercomparison of remotely sensed soil moisture products at various spatial scales over the Iberian Peninsula , 2014 .

[60]  Martha C. Anderson,et al.  Use of NDVI and Land Surface Temperature for Drought Assessment: Merits and Limitations , 2010 .

[61]  Thomas J. Schmugge,et al.  Remote estimation of soil moisture availability and fractional vegetation cover for agricultural fields , 1990 .

[62]  I. Rodríguez‐Iturbe,et al.  Soil Water Balance and Ecosystem Response to Climate Change , 2004, The American Naturalist.

[63]  Zhanqing Li,et al.  Estimation of evaporative fraction from a combination of day and night land surface temperatures and NDVI: A new method to determine the Priestley-Taylor parameter , 2006 .

[64]  C. Woodcock,et al.  Multiscale analysis and validation of the MODIS LAI product: II. Sampling strategy , 2002 .

[65]  Alexander Loew,et al.  Estimation of evapotranspiration from MODIS TOA radiances in the Poyang Lake basin, China , 2012 .

[66]  J. Schmetz,et al.  AN INTRODUCTION TO METEOSAT SECOND GENERATION (MSG) , 2002 .

[67]  M. S. Moran,et al.  Estimating crop water deficit using the relation between surface-air temperature and spectral vegetation index , 1994 .

[68]  Y. Kerr,et al.  Evaluation of remotely sensed and modelled soil moisture products using global ground-based in situ observations , 2012 .

[69]  Hirofumi Hashimoto,et al.  Monitoring and forecasting ecosystem dynamics using the Terrestrial Observation and Prediction System (TOPS) , 2009 .

[70]  Joan M. Galve,et al.  Temperature‐based and radiance‐based validations of the V5 MODIS land surface temperature product , 2009 .

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

[72]  J. Zeng,et al.  Evaluation of remotely sensed and reanalysis soil moisture products over the Tibetan Plateau using in-situ observations , 2015 .

[73]  José Martínez-Fernández,et al.  Temporal Stability of Soil Moisture in a Large‐Field Experiment in Spain , 2003 .

[74]  A. Robock,et al.  The International Soil Moisture Network: a data hosting facility for global in situ soil moisture measurements , 2011 .

[75]  Wim G.M. Bastiaanssen,et al.  Remote sensing for irrigated agriculture: examples from research and possible applications , 2000 .

[76]  Wouter Dorigo,et al.  Potential and limitations of multidecadal satellite soil moisture observations for selected climate model evaluation studies , 2013 .

[77]  A. Cazenave,et al.  The ESA Climate Change Initiative: Satellite Data Records for Essential Climate Variables , 2013 .

[78]  Wade T. Crow,et al.  Potential for downscaling soil moisture maps derived from spaceborne imaging radar data , 2000 .

[79]  Alfonso Calera,et al.  Combining remote sensing and in situ soil moisture data for the application and validation of a distributed water balance model (HIDROMORE) , 2010 .

[80]  W. Wagner,et al.  Soil moisture estimation through ASCAT and AMSR-E sensors: An intercomparison and validation study across Europe , 2011 .

[81]  P. Houser,et al.  Assimilation and downscaling of satellite observed soil moisture over the Little River Experimental Watershed in Georgia, USA , 2013 .

[82]  Yann Kerr,et al.  Downscaling SMOS-Derived Soil Moisture Using MODIS Visible/Infrared Data , 2011, IEEE Transactions on Geoscience and Remote Sensing.

[83]  V. Salomonson,et al.  MODIS: advanced facility instrument for studies of the Earth as a system , 1989 .

[84]  V. Singh,et al.  Deriving theoretical boundaries to address scale dependencies of triangle models for evapotranspiration estimation , 2012 .

[85]  Matthias Drusch,et al.  Global Automated Quality Control of In Situ Soil Moisture Data from the International Soil Moisture Network , 2013 .

[86]  Jie Wang,et al.  Evaluation of Satellite and Reanalysis Soil Moisture Products over Southwest China Using Ground-Based Measurements , 2015, Remote. Sens..

[87]  José Martínez-Fernández,et al.  Analysis of rainfall trends and dry periods on a pluviometric gradient representative of Mediterranean climate in the Duero Basin, Spain , 2004 .

[88]  Ainong Li,et al.  A Downscaling Method for Improving the Spatial Resolution of AMSR-E Derived Soil Moisture Product Based on MSG-SEVIRI Data , 2013, Remote. Sens..

[89]  Regino Zamora,et al.  Seedling establishment of a boreal tree species (Pinus sylvestris) at its southernmost distribution limit: consequences of being in a marginal Mediterranean habitat , 2004 .