Resolution and Accuracy of GPS-Based Terrestrial Water Storage Anomalies During Hydrologic Extremes: Linking Hydrologic Process, Solid-Earth Response, and Monitoring Networks

Abstract:

Observations of TWS anomalies are critical for understanding the terrestrial water cycle, specifically its role within the Earth System, and how it responds to natural and anthropogenic forcing. Existing tools for monitoring TWS anomalies are not optimal for all hydrologic applications. Recently, GPS observations of land surface vertical displacement have been used in novel ways to quantify the spatial and temporal variations of TWS anomalies associated with groundwater mining, seasonal snowpack, and drought. These results suggest that GPS-based records of displacement could greatly expand monitoring of the terrestrial water cycle, complementing and augmenting the information currently provided by in situ observations and GRACE-based estimates. However, none of the studies to date have quantified the errors in TWS anomalies estimated from GPS observations. We are using a forward model for the elastic response to loading driven by realistic TWS anomalies from National Land Data Assimilation System (NLDAS) output to gauge the resolution and accuracy of GPS-based TWS anomalies. In addition to quantifying the total error associated with estimating TWS anomalies from GPS displacements, the artificial simulation framework provides information on how errors are related to interactions between hydrologic process, the solid earth response, and the monitoring network at the continental scale. This research is a necessary first step towards applying these data to a range of hydrologic problems.