Articles | Volume 20, issue 2
Hydrol. Earth Syst. Sci., 20, 605–624, 2016
Hydrol. Earth Syst. Sci., 20, 605–624, 2016

Research article 03 Feb 2016

Research article | 03 Feb 2016

The effect of assimilating satellite-derived soil moisture data in SiBCASA on simulated carbon fluxes in Boreal Eurasia

M. K. van der Molen1, R. A. M. de Jeu2,3, W. Wagner4, I. R. van der Velde1, P. Kolari5, J. Kurbatova6, A. Varlagin6, T. C. Maximov7, A. V. Kononov7, T. Ohta8, A. Kotani8, M. C. Krol1, and W. Peters1,9 M. K. van der Molen et al.
  • 1Meteorology and Air Quality group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, the Netherlands
  • 2VU University Amsterdam, Department of Earth Sciences, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands
  • 3Transmissivity B. V., Space Technology Centre, Huygensstraat 34, Noordwijk, the Netherlands
  • 4Vienna University of Technology, Department of Geodesy and Geoinformation, Gusshausstrasse 27–29, 1040 Vienna, Austria
  • 5Department of Physics, University of Helsinki, P.O. Box 48, Erik Palménin aukio 1, 00014 Helsinke, Finland
  • 6A. N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, Leninsky Prospekt 33, 119071 Moscow, Russia
  • 7Institute for Biological Problems of the Cryolithozone, 677980, 41 Lenin Ave., Yakutsk, Republic of Sakha (Yakutia), Russia
  • 8Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
  • 9Centre for Isotope Research, Energy and Sustainability Research Institute Groningen, Groningen University, Groningen, the Netherlands

Abstract. Boreal Eurasia is a region where the interaction between droughts and the carbon cycle may have significant impacts on the global carbon cycle. Yet the region is extremely data sparse with respect to meteorology, soil moisture, and carbon fluxes as compared to e.g. Europe. To better constrain our vegetation model SiBCASA, we increase data usage by assimilating two streams of satellite-derived soil moisture. We study whether the assimilation improved SiBCASA's soil moisture and its effect on the simulated carbon fluxes. By comparing to unique in situ soil moisture observations, we show that the passive microwave soil moisture product did not improve the soil moisture simulated by SiBCASA, but the active data seem promising in some aspects. The match between SiBCASA and ASCAT soil moisture is best in the summer months over low vegetation. Nevertheless, ASCAT failed to detect the major droughts occurring between 2007 and 2013. The performance of ASCAT soil moisture seems to be particularly sensitive to ponding, rather than to biomass. The effect on the simulated carbon fluxes is large, 5–10 % on annual GPP and TER, tens of percent on local NEE, and 2 % on area-integrated NEE, which is the same order of magnitude as the inter-annual variations. Consequently, this study shows that assimilation of satellite-derived soil moisture has potentially large impacts, while at the same time further research is needed to understand under which conditions the satellite-derived soil moisture improves the simulated soil moisture.

Short summary
Boreal Eurasia contains extensive forests, which play an important role in the terrestrial carbon cycle. Droughts can modify this cycle considerably, although very few ground-based observations are available in the region. We test whether satellite-observed soil moisture may be used to improve carbon cycle models in this region. This paper explains when and where this works best. The interpretation of satellite soil moisture is best in summer conditions, and is hampered by snow, ice and ponding.