GPS Recovery of Daily Hydrologic and Atmospheric Mass Variation: A Methodology and Results From the Australian Continent

Abstract

We present a methodology to invert a regional set of vertical displacement data from Global Positioning System (GPS) to determine the surface mass redistribution. It is assumed that GPS deformation is a result of the Earth's elastic response to the surface mass load of hydrology, atmosphere, and/or ocean. We develop an algorithm to estimate the spectral information of displacements from “regional” GPS data through regional spherical (Slepian) basis functions and apply the load Love numbers to estimate the mass load. The same approach is applied to determine global mass changes from “global” geopotential change data of Gravity Recovery and Climate Experiment (GRACE). We rigorously examine all systematic errors caused by various truncations (spherical harmonic series and Slepian series) and the smoothing constraint applied to the GPS inversion. We demonstrate the technique by processing 16 years of daily vertical motions determined from 114 GPS stations in Australia. The GPS‐inverted surface mass changes are validated against GRACE data, atmosphere and ocean models, and a land surface model. Seasonal and interannual terrestrial mass variations from GPS are in good agreement with GRACE data and the water storage models. The GPS recovery compares better with the water storage model around the smaller coastal basins than two different GRACE solutions. The submonthly mass changes from GPS provide meaningful results agreeing with atmospheric mass changes in central Australia. Finally, it is suggested to integrate GPS and GRACE data to draw a comprehensive picture of daily mass changes on different continents.

A Review of GNSS/GPS in Hydrogeodesy: Hydrologic Loading Applications and Their Implications for Water Resource Research

“…A few recent hydrogeodetic studies have inverted GNSS displacements to estimate high‐frequency TWS changes at timescales as short as 1 day (Han & Razeghi, 2017; Jiang et al., 2021; Milliner et al., 2018; Zhan et al., 2021). For instance, Milliner et al.…”

“…A few recent hydrogeodetic studies have inverted GNSS displacements to estimate high-frequency TWS changes at timescales as short as 1 day ( Han & Razeghi, 2017;Jiang et al, 2021;Milliner et al, 2018;Zhan et al, 2021 ). For instance, Milliner et al ( 2018 ) quantified flood volumes as daily changes in water storage during and following Hurricane Harvey and tracked the movement of stormwaters using 198 GNSS stations in the Southern Texas and Louisiana region, USA.…”

Inversion of GNSS Vertical Displacements for Terrestrial Water Storage Changes Using Slepian Basis Functions

“…For the SBF method, Han and Razeghi (2017) first introduced the SBF into the inversion of surface mass changes using GNSS vertical displacements in the Australian continent, and the results demonstrated that the GNSS‐inverted surface mass changes were in good agreement with the GRACE and hydrologic model estimates. Based on the research of Han and Razeghi (2017), Jiang, Hsu, Yuan, Cheng, et al. (2021), and Jiang et al.…”

Assimilation of Ground‐Based GPS Observations of Vertical Displacement into a Land Surface Model to Improve Terrestrial Water Storage Estimates

“…An alternative approach to the study of TWS is to employ ground‐based Global Positioning System (GPS) observations of surface displacement (most notably vertical displacement) based on the elastic response of the Earth’s surface to mass redistribution (Argus et al., 2017; Borsa et al., 2014; van Dam et al., 2001). Through a comparison of vertical displacements derived from hydrologic models, GRACE, and ground‐based GPS, the capability of ground‐based GPS observations to infer TWS changes has been demonstrated in regions across the globe such as in the Himalayas (Chanard et al., 2014; Fu & Freymueller, 2012; Zhang et al., 2018), the western United States (Knappe et al., 2019; Tan et al., 2016; Wahr et al., 2013; Yin et al., 2020), the North China Plain (Wang et al., 2017), and Australia (Han & Razeghi, 2017). A number of studies have attempted to use ground‐based GPS observations of vertical displacement to estimate TWS changes at both regional (Argus et al., 2014, 2017) and continental (Ferreira et al., 2019) scales, and GPS‐based TWS anomalies have been successfully applied to study the impact of drought (Borsa et al., 2014) and hurricanes (Milliner et al., 2018) on the terrestrial water cycle.…”