TUD-L3-EWH_UNC-GRACEv5: Global 0.5°x0.5° monthly equivalent water height user-friendly dataset with comprehensive uncertainty decomposition (ensemble solution spread, AOD1B uncertainty, DDK leakage error, low-degree coefficient treatment, and GIA ensemble error)

This dataset provides gridded Equivalent Water Height (EWH), which are equivalent on land to Terrestrial Water Storage Anomalies (TWSA) from GRACE and GRACE-FO generated at TU Delft (“TUD”), filtered using the DDK{i} (i=2,...,7) decorrelation filter (Kusche et al., 2009) on a 0.5° × 0.5° global grid. Each file contains monthly fields from 2002–2020. All weighted mean and uncertainty components include gravity signal content from degree 2 to 60. Weights are computed as the normalised square inverses of open-ocean RMS using COST-G RL02.1 (Meyer, U. et al., 2025) monthly solutions as a benchmark. Coefficients C20 and C30 are already replaced using TN-14v3 (https://doi.org/10.1029/2019GL085488). The user can add the geocenter motion (TN-13) contribution (degree-1) separately, as well as remove prominent tidal components (S2, P1, S1, K1, and unmodelled R3), which can be found in the ancillary product TUD-L3-EWH_CLIM-GRACE and TUD-L3-EWH_CLIM_CORR-GRACE.<br>The novelty in this product is the consolidation of multiple official GRACE Level-2 spherical harmonic solutions and their uncertainty propagation into a single multi-component uncertainty budget, which includes:(1) the GIA trend (Bagge, M. et al. 2023),(2) AOD1B (based on AOe07) (Shihora, L. et al. 2024),(3) ensemble solution spread (uncertainty), previously referred to as "solution disparity" (includes effects of parametrisation, and ocean tide models),(4) filtering leakage (Dobslaw, H. et al. 2020), with finally(5) degree-1 uncertainty (Swenson, S., D. Chambers, and J. Wahr, 2008).<br>This layered GRACE(-FO) Level-3 data product provides a comprehensive and transparent view of all uncertainty and post-processing components (including the TUD-L3-EWH_CLIM-GRACE and TUD-L3-EWH_CLIM_LEAKAGE-GRACE product), enabling direct application in data assimilation strategies or other applications. For v3 (onwards) we provide the SLR-free dataset (TUD-L3-EWH_UNC_noSLR-GRACE) for users who wish to perform sensitivity studies. Lastly, for v4/5 we additionally provide the fully application-ready "ewh_mean_corr" (GIA, SLR, degree-1, and tidal aliasing corrected for) variable in the main data product, and the CLIM_CORR associated data product. <br>Details on the data product structure and use can be found at the TUDelft GRACEcube portal:https://grace-cube.lr.tudelft.nl/L2B_UNC/README.html<br>Versioning:v5:(1) since 07 May 2026 from elaborate discussion during EGU26, a decision has been made to defineL3 officially as gridded produtcs (a.k.a. L2/2B Spherical Harmonic coefficients that have been synthesised into the gridded domain).Thus from now on the naming "TUD-L2B-EWH_UNC-GRACE" is translated to TUD-L3-EWH_UNC-GRACE. (2) the website is changed accordingly, with the url link itself kept as is for now.<br>v4:(1) Added fully post-processed (GIA, SLR, degree-1, tidal aliasing removed) EWH called "ewh_mean_corr".(2) Added reconstructed geophysical climatological signal "ewh_mean_clim" in CLIM data products.(3) Added reconstructed tidal aliasing climatological signal "ewh_mean_tides" in CLIM data products.(4) Added CLIM_CORR data product containing full, tidal and residual climatological signals as CLIM. <br>v3:(1) Provided "noSLR" ancillary product for sensitivity analysis.(2) Provided uncertainties from post-fit residuals for climatological products. (3) Period span (i.e. 2002 - 2020) is added directly into the file name convention.<br>v2.0:(1) leakage uncertainty computed using standard deviation (instead of RMS) to have it harmonised with the ensemble mean.(2) "v2.0" added to the name of the data product.(3) the addition of the "residuals" and "t_clim" variables to the ancillary TUD-L2B-EWH_CLIM-GRACEv2.0 product for improved user-friendliness.(4) added leakage climatological ancillary data product: TUD-L2B-EWH_CLIM_LEAKAGE-GRACEv2.0,(5) added propagated uncertainties from replaced SLR C20 and C30 (formal errors),(6) improved README file.<br>v1.0: original dataset.

本数据集提供网格化等效水高（Equivalent Water Height, EWH），在陆地上其物理意义等效于GRACE与GRACE-FO任务反演得到的陆地水储量异常（Terrestrial Water Storage Anomalies, TWSA），由代尔夫特理工大学（TU Delft，简称TUD）生成，并基于DDK{i}（i=2,…,7）去相关滤波器（decorrelation filter，Kusche等，2009）在0.5°×0.5°的全球网格上完成滤波处理。每个文件包含2002年至2020年的逐月场数据。所有加权均值与不确定性分量均涵盖2阶至60阶的重力信号。权重以COST-G RL02.1（Meyer U等，2025）月解作为基准，由开阔洋域均方根误差（Root Mean Square, RMS）的归一化平方倒数计算得到。已使用TN-14v3（https://doi.org/10.1029/2019GL085488）替换了C20与C30系数。用户可自行添加质心运动（TN-13）的一阶（degree-1）贡献，也可去除显著潮汐分量（S2、P1、S1、K1及未建模R3），相关辅助数据可从附属产品TUD-L2B-EWH_CLIM-GRACE与TUD-L2B-EWH_CLIM_CORR-GRACE中获取。
本产品的创新之处在于将多款官方GRACE Level-2球谐解及其不确定性传播整合为单一的多分量不确定性预算体系，具体包含：(1) 冰川均衡调整（Glacial Isostatic Adjustment, GIA）趋势项（Bagge M等，2023）；(2) AOD1B（基于AOe07）（Shihora L等，2024）；(3) 集合解离散度（不确定性），此前被称为“解差异”（涵盖参数化效应与海洋潮汐模型的影响）；(4) 滤波泄漏项（Dobslaw H等，2020）；以及(5) 一阶不确定性（Swenson S、Chambers D与Wahr J，2008）。
这款分层GRACE（-FO）Level-2B数据产品全面且透明地展示了所有不确定性与后处理分量（包括TUD-L2B-EWH_CLIM-GRACE与TUD-L2B-EWH_CLIM_LEAKAGE-GRACE产品），可直接应用于数据同化（data assimilation）策略或其他科研场景。对于v3及后续版本，我们为开展敏感性研究的用户提供了无卫星激光测距（Satellite Laser Ranging, SLR）的数据集（TUD-L2B-EWH_UNC_noSLR-GRACE）。此外，v4版本还在主数据产品中新增了完全就绪的"ewh_mean_corr"变量（已校正GIA、SLR、一阶项与潮汐混叠），并配套推出了CLIM_CORR附属数据产品。
有关本数据产品的结构与使用细节，可访问代尔夫特理工大学GRACEcube门户：https://grace-cube.lr.tudelft.nl/L2B_UNC/README.html。
版本更新日志：
v4：(1) 新增已完成全部后处理（校正GIA、SLR、一阶项与潮汐混叠）的等效水高变量"ewh_mean_corr"；(2) 在CLIM类数据产品中新增重建的地球物理气候信号变量"ewh_mean_clim"；(3) 在CLIM类数据产品中新增重建的潮汐混叠气候信号变量"ewh_mean_tides"；(4) 新增CLIM_CORR附属数据产品，包含完整气候信号、潮汐气候信号与残差气候信号，功能与CLIM产品一致。
v3：(1) 推出用于敏感性分析的"noSLR"附属产品；(2) 为气候类产品提供了后拟合残差得到的不确定性分量；(3) 将数据时段（即2002-2020年）直接纳入文件名命名规则。
v2.0：(1) 采用标准差（而非均方根误差）计算泄漏不确定性，以与集合均值保持一致；(2) 在数据产品名称中添加"v2.0"标识；(3) 在附属产品TUD-L2B-EWH_CLIM-GRACEv2.0中新增"residuals"与"t_clim"变量，提升用户友好性；(4) 新增泄漏气候类附属数据产品TUD-L2B-EWH_CLIM_LEAKAGE-GRACEv2.0；(5) 新增替换后的SLR C20与C30系数的传播不确定性（形式误差）；(6) 优化了README文档。
v1.0：初始版本数据集。