Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2017-760
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
04 Apr 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).
Joint assimilation of soil moisture retrieved from multiple passive microwave frequencies increases robustness and quality of soil moisture state estimation
Anouk I. Gevaert1, Luigi J. Renzullo2,3, Albert I. J. M. van Dijk3, Hans J. van der Woerd4, Albrecht H. Weerts5,6, and Richard A. M. de Jeu7 1Earth and Climate Cluster, Department of Earth Sciences, VU University Amsterdam, Amsterdam, the Netherlands
2CSIRO Land and Water, Canberra, Australia
3Fenner School of Environment and Society, Australia National University, Canberra, Australia
4Institute for Environmental Studies (IVM), VU University Amsterdam, the Netherlands
5Deltares, Delft, the Netherlands
6Department of Environmental Sciences, Wageningen University, the Netherlands
7VanderSat B.V., Haarlem, the Netherlands
Abstract. Soil moisture affects the partitioning of water and energy and is recognized as an essential climate variable. Soil moisture estimates derived from passive microwave remote sensing can improve model estimates through data assimilation, but the relative effectiveness of microwave retrievals in different frequencies is unclear. Land Parameter Retrieval Model (LPRM) satellite soil moisture derived from L-, C- and X-band frequency remote sensing were assimilated in the Australian Water Resources Assessment landscape hydrology model (AWRA-L). Two sets of experiments were performed. First, each retrieval was assimilated individually for comparison. Second, each possible combination of two retrievals was assimilated jointly. Results were evaluated against field-measured top-layer and root-zone soil moisture at 24 sites across Australia. Assimilation generally improved the coefficient of correlation (r) between modelled and field-measured soil moisture. L- and X-band retrievals were more informative than C-band retrievals, improving r by an average of 0.11 and 0.08 compared to 0.04, respectively. Although L-band retrievals were more informative for top-layer soil moisture in most cases, there were exceptions, and L- and X-band were equally informative for root-zone soil moisture. The consistency between L- and X-band retrievals suggests that they can substitute for each other, for example when transitioning between sensors and missions. Furthermore, joint assimilation of retrievals resulted in a model performance that was similar to or better than assimilating either retrieval individually. Comparison of model estimates obtained with global precipitation data and with higher-quality, higher-resolution regional data, respectively, demonstrated that precipitation data quality does determine the overall benefit that can be expected from assimilation. Further work is needed to assess the potentially complementary spatial information that can be derived from retrievals from different frequencies.
Citation: Gevaert, A. I., Renzullo, L. J., van Dijk, A. I. J. M., van der Woerd, H. J., Weerts, A. H., and de Jeu, R. A. M.: Joint assimilation of soil moisture retrieved from multiple passive microwave frequencies increases robustness and quality of soil moisture state estimation, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-760, in review, 2018.
Anouk I. Gevaert et al.
Anouk I. Gevaert et al.
Anouk I. Gevaert et al.

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Short summary
We assimilated three satellite soil moisture retrievals based on different microwave frequencies into a hydrological model. Two sets of experiments were performed, first assimilating the retrievals individually and then assimilating each set of two retrievals jointly. Overall, assimilation improved agreement between model and field-measured soil moisture. Joint assimilation resulted in model performance similar to or better than assimilating either retrieval individually.
We assimilated three satellite soil moisture retrievals based on different microwave frequencies...
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