A new methodology is proposed to estimate changes in the Earth’s dynamic oblateness ($$\Delta {J_{2}}$$ΔJ2 or equivalently, $$-\sqrt{5}\Delta {C_{20}}$$-5ΔC20) on a monthly basis. The algorithm uses monthly Gravity Recovery and Climate Experiment (GRACE) gravity solutions, an ocean bottom pressure model and a glacial isostatic adjustment (GIA) model. The resulting time series agree remarkably well with a solution based on satellite laser ranging (SLR) data. Seasonal variations of the obtained time series show little sensitivity to the choice of GRACE solutions. Reducing signal leakage in coastal areas when dealing with GRACE data and accounting for self-attraction and loading effects when dealing with water redistribution in the ocean is crucial in achieving close agreement with the SLR-based solution in terms of de-trended solutions. The obtained trend estimates, on the other hand, may be less accurate due to their dependence on the GIA models, which still carry large uncertainties.

中文翻译：

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从 GRACE 数据和地球物理模型观察到的地球动态扁率变化

提出了一种估计地球动态扁率变化的新方法（$$\Delta {J_{2}}$$ΔJ2 或等效的 $$-\sqrt{5}\Delta {C_{20}}$$-5ΔC20 ） 在每个月的基础上。该算法使用月度重力恢复和气候实验 (GRACE) 重力解决方案、海底压力模型和冰川均衡调整 (GIA) 模型。由此产生的时间序列与基于卫星激光测距 (SLR) 数据的解决方案非常吻合。获得的时间序列的季节性变化对 GRACE 解决方案的选择几乎不敏感。在处理 GRACE 数据时减少沿海地区的信号泄漏，并在处理海洋中的水重新分配时考虑自吸引和负载效应，对于在去趋势解决方案方面与基于 SLR 的解决方案达成密切一致至关重要。