An overview of the geodetic satellite data contribution in investigating earth's dynamic phenomena at regional and global scales: A case study example

Abstract

Climate change and increasing pressure on natural resources require reliable methods for monitoring environmental and geophysical processes over large areas. This thesis examines the role of satellite data and Earth observation in studying dynamic phenomena occurring within the Earth, with particular attention to the contribution of Geodetic satellite data to climate change and natural resources investigations. The applied part of the thesis focuses on the Euphrates–Tigris Basin during 2003–2021. Total water storage (TWS) was selected as the main variable because it represents the combined water stored in groundwater, soil moisture, surface water, snow, and ice. HydroBASINS data were used in Google Earth Engine to define the basin boundary, GRACE/GRACE-FO mascon data were used to analyze TWS/LWE anomalies, and the ICGEM G3 Browser supported gravity field visualization and analysis of the time series averaged over the basin. This methodological framework allowed the study area to be evaluated from both spatial and temporal perspectives. Google Earth Engine was used to support basin delineation, mapping of mean anomaly conditions, and examination of spatial trends, while ICGEM G3 Browser outputs supported the interpretation of the time series averaged over the basin. These outputs provided a coherent basis for interpreting the spatial distribution, temporal variability, trend behavior, annual changes, and seasonal characteristics of TWS anomalies over the basin. The results show that the basin experienced mainly negative TWS/LWE anomalies during the study period. The mean anomaly value was approximately -4.16 cm, and the monthly time series showed a shift from more positive anomalies in the earlier years toward more frequent negative anomalies in later periods. Linear trend analysis indicated a decreasing tendency, with an approximate annual decline of -0.75 cm/year. Seasonal analysis showed that spring had the highest average TWS anomaly, while autumn had the lowest, reflecting the seasonal behavior of water storage conditions across the basin. These findings demonstrate that GRACE/GRACE-FO satellite gravimetry is a valuable tool for hydrological assessment at the basin level. By providing an integrated view of water storage variability across a large transboundary basin, it helps reveal changes that cannot be fully captured through local observations alone. The thesis shows that Geodetic satellite data and related analysis methods are valuable tools for monitoring processes related to climate change and natural resources and for understanding phenomena occurring within the dynamic Earth.