Articles | Volume 17, issue 10
Hydrol. Earth Syst. Sci., 17, 3707–3720, 2013
Hydrol. Earth Syst. Sci., 17, 3707–3720, 2013

Research article 01 Oct 2013

Research article | 01 Oct 2013

Benchmark products for land evapotranspiration: LandFlux-EVAL multi-data set synthesis

B. Mueller1, M. Hirschi1, C. Jimenez2, P. Ciais3, P. A. Dirmeyer4, A. J. Dolman5, J. B. Fisher6, M. Jung7, F. Ludwig8, F. Maignan3, D. G. Miralles9, M. F. McCabe10, M. Reichstein7, J. Sheffield11, K. Wang12, E. F. Wood11, Y. Zhang13, and S. I. Seneviratne1 B. Mueller et al.
  • 1Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
  • 2LERMA, Observatoire de Paris, Paris, France
  • 3LSCE, UMR CEA-CNRS, Gif-sur-Yvette, France
  • 4George Mason University, Fairfax, Virginia, USA
  • 5VU University Amsterdam, the Netherlands
  • 6Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
  • 7Max Planck Institute for Biogeochemistry, Jena, Germany
  • 8Wageningen University, Wageningen, the Netherlands
  • 9School of Geographical Sciences, University of Bristol, UK
  • 10Water Desalination and Reuse Center, King Abdullah University of Science and Technology, Kingdom of Saudi Arabia
  • 11Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey, USA
  • 12College of Global Change and Earth System Science, Beijing Normal University, Beijing, China
  • 13CSIRO Land and Water, Canberra, Australia

Abstract. Land evapotranspiration (ET) estimates are available from several global data sets. Here, monthly global land ET synthesis products, merged from these individual data sets over the time periods 1989–1995 (7 yr) and 1989–2005 (17 yr), are presented. The merged synthesis products over the shorter period are based on a total of 40 distinct data sets while those over the longer period are based on a total of 14 data sets. In the individual data sets, ET is derived from satellite and/or in situ observations (diagnostic data sets) or calculated via land-surface models (LSMs) driven with observations-based forcing or output from atmospheric reanalyses. Statistics for four merged synthesis products are provided, one including all data sets and three including only data sets from one category each (diagnostic, LSMs, and reanalyses). The multi-annual variations of ET in the merged synthesis products display realistic responses. They are also consistent with previous findings of a global increase in ET between 1989 and 1997 (0.13 mm yr−2 in our merged product) followed by a significant decrease in this trend (−0.18 mm yr−2), although these trends are relatively small compared to the uncertainty of absolute ET values. The global mean ET from the merged synthesis products (based on all data sets) is 493 mm yr−1 (1.35 mm d−1) for both the 1989–1995 and 1989–2005 products, which is relatively low compared to previously published estimates. We estimate global runoff (precipitation minus ET) to 263 mm yr−1 (34 406 km3 yr−1) for a total land area of 130 922 000 km2. Precipitation, being an important driving factor and input to most simulated ET data sets, presents uncertainties between single data sets as large as those in the ET estimates. In order to reduce uncertainties in current ET products, improving the accuracy of the input variables, especially precipitation, as well as the parameterizations of ET, are crucial.