Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2016-558
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
08 Nov 2016
Review status
A revision of this discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Reducing soil moisture measurement scale mismatch to improve surface energy flux estimation
Joost Iwema1, Rafael Rosolem1,2, Mostaquimur Rahman1, Eleanor Blyth3, and Thorsten Wagener1,2 1Department of Civil Engineering, University of Bristol, Bristol, UK
2Cabot Institute, University of Bristol, Bristol, UK
3Centre for Ecology and Hydrology, Wallingford, OX10 8BB, UK
Abstract. At the so-called hyper-resolution scale (i.e. grid cells of 1 km2) Land Surface Model (LSM) parameters are sometimes calibrated with Eddy-Covariance (EC) data and Point Scale (PS) soil moisture data. However, measurement scales of EC and PS data differ substantially. In our study, we investigated the impact of reducing the scale mismatch between surface energy flux data and soil moisture data by replacing PS soil moisture data with observations derived from Cosmic-Ray Neutron Sensors (CRNS) made at larger spatial scales. Five soil-evapotranspiration parameters of the Joint UK Land Environment Simulator (JULES) were calibrated against PS and CRNS soil moisture data separately. We calibrated the model for twelve sites in the USA representing a range of climatic, soil, and vegetation conditions. The improvement in surface energy partitioning for the two calibration solutions was assessed by comparing to EC data and to a version of JULES runs with default parameter values. We found that simulated surface energy partitioning did not differ substantially between the PS and CRNS calibrations, despite their differences in actual soil moisture observations. We concluded that potential differences due to distinct spatial scales represented by the PS and CRNS soil moisture sensor techniques were substantially undermined by the weak coupling between soil moisture and evapotranspiration within JULES.

Citation: Iwema, J., Rosolem, R., Rahman, M., Blyth, E., and Wagener, T.: Reducing soil moisture measurement scale mismatch to improve surface energy flux estimation, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-558, in review, 2016.
Joost Iwema et al.
Joost Iwema et al.
Joost Iwema et al.

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Short summary
We investigated whether the simulation of water flux from the land surface to the atmosphere (using the Joint UK Land Environment Simulator model) could be improved by replacing traditional soil moisture sensor data with data from a the more novel Cosmic-Ray Neutron soil moisture sensor. Despite observed differences between the two types of soil moisture measurement data, we found no substantial differences in improvement in water flux estimation. This seemed to be caused by model properties.
We investigated whether the simulation of water flux from the land surface to the atmosphere...
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