Assessment of Temporal Variations of Orthometric/Normal Heights Induced by Hydrological Mass Variations over Large River Basins Using GRACE Mission Data

Abstract

Almost half of the Earth’s land is covered by large river basins. Temporal variations of hydrological masses induce time-varying gravitational potential and temporal mass loading that deforms the Earth’s surface. These phenomena cause temporal variations of geoid/quasigeoid and ellipsoidal heights that result in temporal variations of orthometric/normal heights ΔH/ΔH*. The aim of this research is to assess ΔH/ΔH* induced by hydrological masses over large river basins using the Gravity Recovery and Climate Experiment (GRACE) satellite mission data. The results obtained reveal that for the river basin of a strong hydrological signal, ΔH/ΔH* reach 8 cm. These ΔH/ΔH* would be needed to reliably determine accurate orthometric/normal heights. The ΔH/ΔH* do not exceed ±1 cm in the case of the river basin of the weak hydrological signal. The relation between hydrological mass changes and ΔH/ΔH* was investigated. Correlations between ΔH/ΔH* and temporal variations of equivalent water thickness were observed in 87% of river basins subareas out of which 45% exhibit strong correlations. The ΔH/ΔH* determined over two river basins that characterize with the strongest and weakest temporal variations were analysed using the Principal Component Analysis method. The results obtained reveal that ΔH/ΔH* in subareas of the same river basin can significantly differ (e.g., ±2 cm in the Amazon basin) from each other, and are strongly associated with different spatio-temporal patterns of the entire river basin.

Research on gravity field modelling and gravimetry in Poland in 2019–2022

“…For the river basin of a weak hydrological signal, such as the Orange river basin, Δ𝐻/Δ𝐻 * do not exceed ±1 cm, while Δ𝐻/Δ𝐻 * can reach 8 cm in the case of the river basin of strong hydrological signal, e.g. the Amazon river basin (Godah et al, 2020c). The analyses of Δ𝐻/Δ𝐻 * obtained indicated that due to spatio-temporal patterns such as unusual floods, extreme drought, and rainfall seasonality within the entire river basin as well as the location of the upstream and downstream areas of the river basin, clear differences (e.g.…”

“…The analyses of Δ𝐻/Δ𝐻 * obtained indicated that due to spatio-temporal patterns such as unusual floods, extreme drought, and rainfall seasonality within the entire river basin as well as the location of the upstream and downstream areas of the river basin, clear differences (e.g. ±2 cm in the Amazon river basin) for Δ𝐻/Δ𝐻 * can be found within subareas of the same river basin (Godah et al, 2020c). For the area of Turkey, the differences between Δ𝐻/Δ𝐻 * in the same area at different epochs reach up to 25 mm, while those differences at the same epoch and different areas reach up to 9 mm (Öztürk et al, 2020).…”

“…Significant efforts of the IGiK's team have been put into the estimation of orthometric/normal height changes (Δ𝐻/Δ𝐻 * ) over 24 large river basins (Godah et al, 2020c) as well as for the areas of Turkey (Öztürk et al, 2020) and Poland (Szelachowska et al, 2022) using GRACE satellite mission data. For the river basin of a weak hydrological signal, such as the Orange river basin, Δ𝐻/Δ𝐻 * do not exceed ±1 cm, while Δ𝐻/Δ𝐻 * can reach 8 cm in the case of the river basin of strong hydrological signal, e.g.…”