Surface Mass Variations from GPS and GRACE/GFO: A Case Study in Southwest China

Abstract

Surface mass variations inferred from the Global Positioning System (GPS), and observed by the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GFO) complement each other in terms of spatial and temporal coverage. This paper presents an analysis of regional surface mass variations inverted from GPS vertical displacements under different density distributions of GPS stations, and compares the GPS-derived mass variations with GRACE/GFO inversion results in spatial and temporal domains. To this end, GPS vertical displacement data from a total of 85 permanent GPS stations of the Crustal Movement Observation Network of China (CMONOC), the latest GRACE/GFO RL06 spherical harmonic (SH) solutions and GRACE RL06 mascon solutions are used to investigate surface mass variations in four regions or basins, including the Yunnan Province (YNP), Min River Basin (MRB), Jialing River Basin (JLRB), and Wu River Basin (WRB) in Southwest China. Our results showed that the spatial distributions and seasonal characteristics of GPS-derived mass change time series agree well with those from GRACE/GFO observations, especially in regions with relatively dense distributions of GPS stations (e.g., in the YNP and MRB), but there are still obvious discrepancies between the GPS and GRACE/GFO results. Scale factor methods (both basin-scaled and pixel-scaled) were employed to reduce the amplitude discrepancies between GPS and GRACE/GFO results. The results also showed that the one-year gap between the GRACE and GFO missions can be bridged by scaled GPS-derived mass change time series in the four studied regions, especially in the YNP and MRB regions (with relatively dense distributions of GPS stations).

Autoregressive Reconstruction of Total Water Storage within GRACE and GRACE Follow-On Gap Period

“…For both cases, there is an apparent decrease in TWS values in the first months of the gap, an increase in the following months, and another decrease after 2018 (Figure 11a). The TWS changes for the Amazon area were also analyzed by combined gravity data [58], and the TWS changes were estimated by the stochastic approach, i.e., the singular spectrum analysis (SSA, [23] or MSSA [59]) methods, in which authors noted similar variations of monthly TWS changes. For Australia, the monthly TWS changes determined by Swarm overestimate the GRACE/-FO TWS and predicted GRACE TWS values (Figure 11b).…”

Estimation of Terrestrial Water Storage Variations in Sichuan-Yunnan Region from GPS Observations Using Independent Component Analysis

“…Zhang et al [16] estimated the annual EWH (equivalent water height) changes of the lower Three-Rivers headwater region in southwestern China using the vertical displacements of GPS time series obtained from the Crustal Movement Observation Network of China (CMONOC). Zhong et al [17] analyzed GPS-inverted mass changes under different density distributions of GPS stations and compared the inversion results with GRACE/GFO solutions in spatial and temporal domains.…”

Improving the Inversion Accuracy of Terrestrial Water Storage Anomaly by Combining GNSS and LSTM Algorithm and Its Application in Mainland China

“…This observation tool can accurately measure the gravity field and continuously monitor changes in surface mass [19]. In recent years, many researchers have studied the redistribution of the water mass in typical regions based on GRACE, such as the Amazon basin [20], Greenland [21], the North China Plain [22], and Southwest China [23]. However, the orbit radius of GRACE satellites leads to inversion results with a coarser spatiotemporal resolution [24].…”