Sensing the Terrestrial and Atmospheric Hydrological Dynamic using Satellite Gravimeter and GNSS

Abstract

Geodetic observation methods, e.g., satellite gravimeter and Global Navigation Satellite System (GNSS), are mainly used for determining the Earth's gravity field and reference system. However, many efforts have been made to adopt the mentioned methods for estimating hydrological dynamics. The satellite gravimeter of the Gravity Recovery and Climate Experiment and its Following-On missions (GRACE/GRACE-FO) have proven to capture the terrestrial hydrological variation. Also, thanks to its signal propagation through the atmosphere medium, GNSS can be used for sensing the hydrology variation in the atmosphere, i.e., troposphere medium. This study aims to explore GRACE/GRACE-FO and GNSS observations to estimate the respective terrestrial and atmospheric hydrological variation in Bandung, Indonesia. Monthly solutions of GRACE/GRACE-FO provided by three agencies were used to estimate the terrestrial hydrological variation. We also used the continuous GNSS site of ITB1 and calculated the atmospheric hydrological series in the form of precipitable water vapor. We found that the terrestrial hydrological series varies approximately ±20 cm, while the precipitable water vapor ranges between 1 to 5 centimeters. Further, we observed long-wavelength components from terrestrial and atmospheric hydrological variations that correspond to dry and wet seasons. However, we only sensed shorter wavelength components of hydrological dynamic from GNSS observation and not for the GRACE as the estimated hydrological variations were estimated monthly. At the same time, delays were calculated every two hours using GNSS observations. Nevertheless, this study shows the potential uses of geodetic approaches such as satellite gravity and GNSS observations to capture the hydrological dynamic.