SUMMARY

We analyse a nearly 8-yr record (2010–2018) of the superconducting gravimeter OSG-060 located at Djougou (Benin, West Africa). After tidal analysis removing all solid Earth and ocean loading tidal contributions and correcting for the long-term instrumental drift and atmospheric loading, we obtain a gravity residual signal which is essentially a hydrological signal due to the monsoon. This signal is first compared to several global hydrology models (ERA, GLDAS and MERRA). Our superconducting gravimeter residual signal is also superimposed onto episodic absolute gravity measurements and to space gravimetry GRACE data. A further comparison is done using local hydrological data like soil moisture in the very superficial layer (0–1.2 m), water table depth and rainfall. The temporal evolution of the correlation coefficient between the gravity observation and both the soil moisture and the water table is well explained by the direct infiltration process of rain water together with the lateral transfer discharging the water table.Finally, we compute the water storage changes (WSC) using a simulation based on the physically based Parflow-CLM numerical model of the catchment, which solves the water and energy budget from the impermeable bedrock to the top of the canopy layer using the 3-D Richards equation for the water transfers in the ground, the kinematic wave equation for the surface runoff and a land surface model (CLM) for the energy budget and evapotranspiration calculation.This model forced by rain is in agreement with evapotranspiration and stream flow data and leads to simulated water storage changes that nicely fit to the observed gravity signal. This study points out the important role played by surface gravity changes in terms of a reliable proxy for water storage changes occurring in small catchments.

中文翻译：

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利用Djougou（西非贝宁）超导重力仪OSG-060的8年记录（2010-2018）对季风水文贡献进行了研究

概要

我们分析了位于Djougou（西非贝宁）的超导重力仪OSG-060的近8年记录（2010-2018年）。经过潮汐分析，除去了所有固体和海洋载荷的潮汐贡献，并校正了长期的仪器性漂移和大气载荷，我们获得了重力残余信号，该信号本质上是由于季风引起的水文信号。首先将该信号与几种全球水文模型（ERA，GLDAS和MERRA）进行比较。我们的超导重力仪残留信号也被叠加到间歇式绝对重力测量值和空间重力GRACE数据上。使用当地的水文数据（例如，非常浅层的土壤湿度（0-1.2 m），地下水位深度和降雨）进行了进一步的比较。受雨强迫的该模型与蒸散量和水流数据一致，并且导致模拟的储水量变化非常适合观测到的重力信号。这项研究指出了地表重力变化的重要作用，它是小流域发生的蓄水量变化的可靠代表。