The global navigation satellite system (GNSS) and gravity recovery and climate experiment (GRACE) are two independent geodetic technologies that can detect geometric and gravity deformations, respectively. The signals observed by the two technologies mainly include the internal tectonic movement and surface mass loading effects. The former generally exhibits a long-term stable linear trend, whereas the latter exhibits strong seasonality. Many studies have compared seasonal deformations between GRACE and GNSS or combined them to study the water cycle or tectonic signals. However, whether GRACE and GNSS are comparable and what the magnitude of their differences still remain unclear. In this study, we present simulations and a case study of the Amazon basin to address this ambiguity. The loading deformations were simulated in response to load masses with varying resolutions and distributions. We found that the discrepancy is about 30% in the spatial average between the accurate loading displacement and the truncated-result at degree-60 after applying a G300 or DDK4 filter due to a single load mass. The simulated horizontal deformation may have larger discrepancies at a single point in response to the chessboard mass distributions. The case study in the Amazon basin basically verifies our simulation results, which indicate that there is an ∼40%–50% discrepancy between the GNSS-observed and GRACE-modeled displacements spatial average, and it may reach several times that at a single point. We demonstrate that the difference between the GRACE and GNSS is significant for both regional average and single-point analyses.

中文翻译：

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考虑区域平均值和离散点的 GRACE 和 GNSS 季节性载荷位移的比较

全球导航卫星系统（GNSS）和重力恢复与气候实验（GRACE）是两种独立的大地测量技术，可以分别检测几何变形和重力变形。两种技术观测到的信号主要包括内部构造运动和地表物质加载效应。前者一般表现出长期稳定的线性趋势，而后者表现出很强的季节性。许多研究比较了 GRACE 和 GNSS 之间的季节性变形，或将它们结合起来研究水循环或构造信号。然而，GRACE 和 GNSS 是否具有可比性以及它们的差异程度仍不清楚。在这项研究中，我们展示了亚马逊盆地的模拟和案例研究，以解决这种歧义。载荷变形是根据不同分辨率和分布的载荷质量模拟的。我们发现，由于单个负载质量，在应用 G300 或 DDK4 滤波器后，精确负载位移与 60 度的截断结果之间的空间平均值差异约为 30%。响应于棋盘质量分布，模拟的水平变形在单个点处可能具有更大的差异。亚马逊流域的案例研究基本验证了我们的模拟结果，表明GNSS观测和GRACE模型位移空间平均值之间存在~40%~50%的差异，并且可能达到单点的数倍. 我们证明 GRACE 和 GNSS 之间的差异对于区域平均分析和单点分析都很重要。