Data for: Filling the data gaps within GRACE missions using Singular Spectrum Analysis

Dozens of missing epochs in the monthly gravity product of the satellite mission Gravity Recovery and Climate Experiment (GRACE) and its follow-on (GRACE-FO) mission greatly inhibit the complete analysis and full utilization of the data. Despite previous attempts to handle this problem, a general all-purpose gap-filling solution is still lacking. Here we propose a non-parametric, data-adaptive and easy-to-implement approach - composed of the Singular Spectrum Analysis (SSA) gap-filling technique, cross-validation, and spectral testing for significant components - to produce reasonable gap-filling results in the form of spherical harmonic coefficients (SHCs). We demonstrate that this approach is adept at inferring missing data from long-term and oscillatory changes extracted from available observations. A comparison in the spectral domain reveals that the gap-filling result resembles the product of GRACE missions below spherical harmonic degree 30 very well. As the degree increases above 30, the amplitude per degree of the gap-filling result decreases more rapidly than that of GRACE/GRACE-FO SHCs, showing effective suppression of noise. As a result, our approach can reduce noise in the oceans without sacrificing resolutions on land. The gap filling dataset is stored in the “SSA_filing/" folder. Each file represents a monthly result in the form of spherical harmonics. The data format follows the convention of the site ftp://isdcftp.gfz-potsdam.de/grace/. Low degree corrections (degree-1, C20, C30) have been made. The code to generate the dataset is located in the “code_share/“ folder, with an example for C30. The model-based Greenland mass balance result for data validation (results given in the paper) is provided in the "Greenland_SMB-D.txt” file.

在卫星任务重力恢复和气候实验（GRACE）及其后续任务（GRACE-FO）的月度重力产品中，存在数十个缺失的周期，这极大地阻碍了数据的全面分析和充分利用。尽管之前尝试解决这一问题，但仍然缺乏一种通用的全功能插补方案。在此，我们提出了一种非参数、数据自适应且易于实施的解决方案——由奇异谱分析（SSA）插补技术、交叉验证和显著成分的频谱测试组成——以生成合理的球形谐振系数（SHCs）形式的插补结果。我们证明，该方法擅长从可观测的长期和振荡变化中推断缺失数据。在频谱域的比较中显示，插补结果与GRACE任务在球形谐振阶数30以下的产品非常相似。随着阶数超过30，插补结果的每阶幅度比GRACE/GRACE-FO SHCs下降更快，显示出有效抑制噪声的能力。因此，我们的方法可以在不牺牲陆地分辨率的情况下减少海洋中的噪声。插补数据集存储在“SSA_filing/”文件夹中。每个文件以球形谐振的形式代表一个月的结果。数据格式遵循ftp://isdcftp.gfz-potsdam.de/grace/的站点约定。对低阶修正（阶数-1，C20，C30）已进行。生成数据集的代码位于“code_share/”文件夹中，其中包含C30的示例。提供在“Greenland_SMB-D.txt”文件中的基于模型的格陵兰质量平衡结果，以供数据验证（文中给出的结果）使用。