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

Almost half of the Earth&rsquo
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&rsquo
s surface. These phenomena cause temporal variations of geoid/quasigeoid and ellipsoidal heights that result in temporal variations of orthometric/normal heights &Delta
H/&Delta
H*. The aim of this research is to assess &Delta
H* 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, &Delta
H* reach 8 cm. These &Delta
H* would be needed to reliably determine accurate orthometric/normal heights. The &Delta
H* do not exceed &plusmn
1 cm in the case of the river basin of the weak hydrological signal. The relation between hydrological mass changes and &Delta
H* was investigated. Correlations between &Delta
H* and temporal variations of equivalent water thickness were observed in 87% of river basins subareas out of which 45% exhibit strong correlations. The &Delta
H* 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 &Delta
H* in subareas of the same river basin can significantly differ (e.g., &plusmn
2 cm in the Amazon basin) from each other, and are strongly associated with different spatio-temporal patterns of the entire river basin.