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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 5 | Copyright
Geosci. Model Dev., 10, 1903-1925, 2017
https://doi.org/10.5194/gmd-10-1903-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Model description paper 17 May 2017

Model description paper | 17 May 2017

GLEAM v3: satellite-based land evaporation and root-zone soil moisture

Brecht Martens1, Diego G. Miralles1,2, Hans Lievens1,3, Robin van der Schalie4,2, Richard A. M. de Jeu4, Diego Fernández-Prieto5, Hylke E. Beck6, Wouter A. Dorigo7,1, and Niko E. C. Verhoest1 Brecht Martens et al.
  • 1Laboratory of Hydrology and Water Management, Ghent University, Coupure links 653, 9000 Ghent, Belgium
  • 2Department of Earth Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085–1087, 1081 HV Amsterdam, the Netherlands
  • 3Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, 20771 Maryland, USA
  • 4Transmissivity/VanderSat B.V., Space Technology Center, Huygensstraat 34, 2201 DK Noordwijk, Netherlands
  • 5European Space Research Institute (ESRIN), European Space Agency (ESA), Via Galileo Galilei 64, 00044 Frascati, Italy
  • 6Joint Research Centre (JRC), European Comission, Via Enrico Fermi 2749, 21027 Ispra, Italy
  • 7Department of Geodesy and Geo-Information, Vienna University of Technology, Gußhausstraße 25–29, 1040 Vienna, Austria

Abstract. The Global Land Evaporation Amsterdam Model (GLEAM) is a set of algorithms dedicated to the estimation of terrestrial evaporation and root-zone soil moisture from satellite data. Ever since its development in 2011, the model has been regularly revised, aiming at the optimal incorporation of new satellite-observed geophysical variables, and improving the representation of physical processes. In this study, the next version of this model (v3) is presented. Key changes relative to the previous version include (1) a revised formulation of the evaporative stress, (2) an optimized drainage algorithm, and (3) a new soil moisture data assimilation system. GLEAM v3 is used to produce three new data sets of terrestrial evaporation and root-zone soil moisture, including a 36-year data set spanning 1980–2015, referred to as v3a (based on satellite-observed soil moisture, vegetation optical depth and snow-water equivalent, reanalysis air temperature and radiation, and a multi-source precipitation product), and two satellite-based data sets. The latter share most of their forcing, except for the vegetation optical depth and soil moisture, which are based on observations from different passive and active C- and L-band microwave sensors (European Space Agency Climate Change Initiative, ESA CCI) for the v3b data set (spanning 2003–2015) and observations from the Soil Moisture and Ocean Salinity (SMOS) satellite in the v3c data set (spanning 2011–2015). Here, these three data sets are described in detail, compared against analogous data sets generated using the previous version of GLEAM (v2), and validated against measurements from 91 eddy-covariance towers and 2325 soil moisture sensors across a broad range of ecosystems. Results indicate that the quality of the v3 soil moisture is consistently better than the one from v2: average correlations against in situ surface soil moisture measurements increase from 0.61 to 0.64 in the case of the v3a data set and the representation of soil moisture in the second layer improves as well, with correlations increasing from 0.47 to 0.53. Similar improvements are observed for the v3b and c data sets. Despite regional differences, the quality of the evaporation fluxes remains overall similar to the one obtained using the previous version of GLEAM, with average correlations against eddy-covariance measurements ranging between 0.78 and 0.81 for the different data sets. These global data sets of terrestrial evaporation and root-zone soil moisture are now openly available at www.GLEAM.eu and may be used for large-scale hydrological applications, climate studies, or research on land–atmosphere feedbacks.

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Terrestrial evaporation is a key component of the hydrological cycle and reliable data sets of this variable are of major importance. The Global Land Evaporation Amsterdam Model (GLEAM, www.GLEAM.eu) is a set of algorithms which estimates evaporation based on satellite observations. The third version of GLEAM, presented in this study, includes an improved parameterization of different model components. As a result, the accuracy of the GLEAM data sets has been improved upon previous versions.
Terrestrial evaporation is a key component of the hydrological cycle and reliable data sets of...
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