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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Discussion papers | Copyright
https://doi.org/10.5194/hess-2018-440
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 27 Aug 2018

Research article | 27 Aug 2018

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This discussion paper is a preprint. It is a manuscript under review for the journal Hydrology and Earth System Sciences (HESS).

Exploring the use of a superconducting gravimeter to evaluate radar estimates of heavy rainfall

Laurent Delobbe1, Arnaud Watlet2, Svenja Wilfert3, and Michel Van Camp2 Laurent Delobbe et al.
  • 1Royal Meteorological Institute of Belgium, Brussels, B-1180, Belgium
  • 2Royal Observatory of Belgium, Brussels, B-1180, Belgium
  • 3Institute of Geography, University of Augsburg, Germany

Abstract. The radar-based estimation of intense precipitation produced by convective storms is a challenging task and the verification through comparison with gauges is questionable due to the very high spatial variability of such type of precipitation. In this study, we explore the potential benefit of using a superconducting gravimeter as a new source of in-situ observations for the evaluation of radar-based precipitation estimates. The superconducting gravimeter used in this study is installed in Membach (BE), 48m underneath the surface, at 85km distance from a C-band weather radar located in Wideumont (BE). The 15-year observation record 2003–2017 is available for both gravimeter and radar with 1-min and 5-min time steps, respectively. The gravimeter integrates soil water in a radius of about 400m around the instrument. This allows capturing rainfall at larger spatial scale than traditional rain gauges. The precision of the gravimeter is a few nm/s2; 1nm/s2 corresponding to 2.6mm of water. The comparison of reflectivity and gravity time series for short duration intense rainfall events shows that reflectivity peaks larger than 40dBZ are associated with a rapid decrease of the underground measured gravity. A remarkable correspondence between radar and gravimeter time series is found. The precipitation amounts derived from gravity measurements and from radar observations are further compared for 505 rainfall events. A correlation coefficient of 0.58, a mean bias (radar/gravimeter) of 1.24 and a mean absolute difference (MAD) of 3.19mm are obtained. A better agreement is reached when applying a hail correction by truncating reflectivity values to a given threshold. No bias, a correlation coefficient of 0.64 and a MAD of 2.3mm are reached using a 48-dBZ threshold. The added value of underground gravity measurements as verification dataset is discussed. The two main benefits are the spatial scale at which precipitation is captured and the interesting property that gravity measurements are directly influenced by water mass at ground no matter the type of precipitation: hail or rain.

Laurent Delobbe et al.
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Laurent Delobbe et al.
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Short summary
In this study, we explore the use of an underground superconducting gravimeter as a new source of in-situ observations for the evaluation of radar-based precipitation estimates. The comparison of radar and gravity time series over 15 years shows that short duration intense rainfall events cause a rapid decrease of the measured gravity. Rainfall amounts can be derived from this decrease. The gravimeter allows capturing rainfall at much larger spatial scale than a traditional rain gauge.
In this study, we explore the use of an underground superconducting gravimeter as a new source...
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