联合GNSS与GRACE/GRACE-FO数据反演中国西南地区陆地水储量变化

Joint inversion of GNSS and GRACE/GRACE-FO data for terrestrial water storage changes in Southwest China

GNSS和重力恢复与气候试验(GRACE)及其后续任务(GRACE-FO)给陆地水储量变化(TWSC)研究带来了技术革新,但这两种技术估计的区域TWSC具有不同的时空尺度和精度特性。因此,有必要融合两种观测数据,以获得同一尺度且高精度的TWSC。本文基于GNSS独立反演模型,使用求和算子对喷气推进实验室(JPL)的GRACE/GRACE-FO Mascon数据进行求和运算来构建约束,通过赤池贝叶斯准则选择最优模型参数,构建了一种联合GNSS与GRACE/GRACE-FO数据的区域TWSC反演模型。随后,本文设计数值模拟试验,以验证利用该模型反演中国西南地区TWSC的可行性。结果显示,1000次试验中联合反演估算的均方根误差均值为10 mm,比GNSS独立反演结果低47%。基于此方法,本文联合GNSS与JPL Mascon数据反演了中国西南地区2011年1月—2022年6月的时变TWSC。对比联合反演、GNSS独立反演、GRACE/GRACE-FO和高分辨率全球陆地数据同化系统(GLDAS)的结果,发现联合反演与GLDAS的TWSC周年振幅空间分布特征最吻合,表明联合反演估计的TWSC空间分辨率优于GNSS独立反演和GRACE的结果。最后,结合水平衡方程估算的区域水文收支情况,并通过广义三角帽方法评估陆地水储量等效水柱高的变化率(d(EWH)/d t)的不确定性。结果显示,联合反演估计的d(EWH)/d t不确定性为8 mm/月,较GRACE/GRACE-FO、GNSS独立反演和水平衡方程结果分别低33%、68%和62%。研究结果表明,与GNSS和GRACE/GRACE-FO独立反演方法相比,联合反演能够改善TWSC估值的精度,可为水资源管理决策及水文气候学研究提供更可靠的数据支撑。

The global navigation satellite system(GNSS)and gravity recovery and climate experiment(GRACE),along with its follow-on mission(GRACE-FO)have revolutionized studies of terrestrial water storage changes(TWSC).However,TWSC estimates obtained from these two techniques exhibit different characteristics and accuracy in terms of temporal and spatial scales.Therefore,it is crucial to integrate these observations to obtain high-precision TWSC at a consistent scale.In this study,we designed a joint inversion model that combines GNSS and GRACE/GRACE-FO data for regional TWSC based on the GNSS inversion model(GNSS-IM).The summation operator was used for the Jet Propulsion Laboratory(JPL)GRACE/GRACE-FO Mascon data to construct constraints in the joint inversion model.The optimal model parameters were selected using the Akaike s Bayesian information criterion.To confirm the feasibility of the joint inversion model for estimating TWSC in Southwestern China,we conducted 1000 simulation experiments.The simulation results indicate that the joint inversion yields an average root mean square error of 10 mm,which is 47%lower than that of GNSS-IM.Subsequently,we applied the joint inversion to estimate the TWSC in Southwest China from January 2011 to June 2022,utilizing GNSS and JPL Mascon data.The comparison of the joint inversion results with the results of GNSS-IM,GRACE/GRACE-FO,and the high-resolution global land data assimilation system(GLDAS)shows that the TWSC annual amplitudes of the joint inversion exhibit the most consistent spatial distribution characteristics with those of GLDAS.It indicates that the joint inversion achieves better spatial resolution for TWSC compared to GNSS-IM and GRACE/GRACE-FO.Furthermore,we estimated the regional hydrological budget through the water balance equation and evaluated the uncertainty of the monthly rate of equivalent water height(d(EWH)/d t)of TWSC using the generalized three-cornered hat method.The results demonstrate that the uncertainty of d(EWH)/d t estimated by the joint inversion is 8 mm/month,which is 33%,68%,and 62%lower than the results of GRACE/GRACE-FO,GNSS-IM,and the water balance equation,respectively.Our study indicates that the joint inversion approach improves the accuracy of TWSC compared to GNSS and GRACE/GRACE-FO,and provides more reliable data for water resources management and hydrology research.