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

Abstract

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), 48 m underneath the surface, at 85 km 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 400 m 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; 1 nm/s2 corresponding to 2.6 mm of water. The comparison of reflectivity and gravity time series for short duration intense rainfall events shows that reflectivity peaks larger than 40 dBZ 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 3.19 mm 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 2.3 mm 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.

A Novel Metaheuristic Strategy for the Elucidation of Gravity Anomalies with Application to Geothermal Energy Investigations and Volcanic Activity Studies: Hunger Games Search (HGS)

“…The gravity method in geophysics, a traditional, passive, non-invasive, and costefficient method, measuring the variation in the Earth's gravitational field caused by the difference of rock mass properties at a certain position, has been applied in a large spectrum of projects such as ore/mineral exploration (Hinze, 2013;Chen et al, 2015;Li et al, 2019; Essa and Abo-Ezz, 2021) [1][2][3][4] , archaeology investigation (Branston and Styles, 2006;Batayneh et al, 2010; Sarlak and Aghajani, 2017) [5][6][7] , radioactive waste management (An et al, 2013) [8] , weapons and unexploded ordnances detection (Abedi et al, 2014) [9] , Hydrocarbon/reservoir (oil and gas) recognition (Yuan et al, 2018; Saghafi and Yarveicy, 2019; Cho et al, 2020) [10][11][12] , geothermal energy and volcanic activity study (Altwegg et al, 2015; Uwiduhaye et al, 2018; Essa and Diab, 2022) [13][14][15] , underground cavities or tunnels identification (Pazzi et [16][17][18] , geotechnical and engineering application (Debeglia and Dupont, 2002;Arisona et al, 2018) [19,20] , groundwater monitoring (Frappart and Ramillien, 2018; Delobbe et al, 2018) [21,22] , landfills mapping (Silva et al, 2009;Dumont et al, 2017) [23,24] , subsurface structures imaging...…”