An improved GRACE-derived groundwater storage anomaly (igGWSA) dataset over global land with consideration of most non-groundwater components

Accurate monitoring of global groundwater storage anomaly (GWSA) is imperative for global water security and socio-economic sustainability. The Gravity Recovery and Climate Experiment (GRACE) satellite has emerged as a prevailing methodology for estimating GWSA by deducting non-groundwater components from terrestrial water storage anomaly (TWSA). However, in most previous studies, the accuracy of GWSA estimation suffers from inadequate consideration of non-groundwater components. Here we present an improved GRACE-derived GWSA dataset spanning 2000–2019 at the global scale, namely igGWSA, by taking into account most non-groundwater components including glaciers, permafrost, snow, lakes, reservoirs, profile soil moisture, and plant canopy water. igGWSA demonstrated strong agreement with well-observed groundwater level and model-simulated GWSA in five globally recognized hotspots of groundwater depletion, with the absolute value of correlation coefficient ranging from 0.94 to 0.99. Compared to igGWSA, inadequate consideration of non-groundwater components poses a significant potential impact on the accuracy of GWSA estimation in glacier-covered regions, permafrost zones, giant lakes, and deep-soil areas. For example, neglecting glaciers and permafrost would erroneously interpret glacier melting and permafrost degradation as part of changes in groundwater storage, respectively. The igGWSA is expected to serve global water security research, especially under a changing environment.精准监测全球地下水储量异常（groundwater storage anomaly, GWSA）对全球水安全与社会经济可持续发展至关重要。重力恢复与气候实验（Gravity Recovery and Climate Experiment, GRACE）卫星已成为估算GWSA的主流手段，其通过从陆地水储量异常（terrestrial water storage anomaly, TWSA）中扣除非地下水组分来实现GWSA反演。然而，既往多数研究中，由于对非地下水组分考虑不足，GWSA估算的精度受到显著制约。本研究构建了一套2000-2019年的全球改进型GRACE衍生地下水储量异常数据集（命名为igGWSA），该数据集充分纳入了冰川、多年冻土、积雪、湖泊、水库、剖面土壤水以及植物冠层水等各类非地下水组分。igGWSA在全球公认的5个地下水枯竭热点区域中，与实测地下水位及模型模拟的GWSA均表现出极强的一致性，相关系数绝对值介于0.94至0.99之间。相较于igGWSA，未充分考虑非地下水组分的传统估算方法，在冰川覆盖区、多年冻土带、大型湖泊区以及深层土壤区域，会对GWSA估算精度造成显著负面影响。例如，忽略冰川与多年冻土组分时，会分别错误地将冰川消融与多年冻土退化归因于地下水储量变化。本数据集有望为全球水安全研究提供有力支撑，尤其是在环境变化背景下的相关研究中。