IB and NIB Hypotheses and their possible discrimination by GRACE

Abstract

The NASA, the GFZ and the DLR plan the GRACE satellite mission to obtain an accurate gravity field after every 2‐4 weeks. Because of its extreme high precision, GRACE is expected to determine the temporal variations of the gravity fields due to time varying geophysical phenomena. Among them, the effects of the atmospheric surface pressure have the largest signals and we investigated its effects mainly from the viewpoint of degree amplitudes. Behaviour of atmospheric variations over oceanic areas is unknown. The response of the ocean is essentially important not only for the corrections of the atmospheric effects on gravity fields, but also for many other studies such as satellite altimetry, crustal deformation and the Earth rotations. We proposed and applied several ocean response models, i.e., IB, NIB, and intermediate ones, and evaluated the degree power differences between each one of them. The results show that almost all the differences are distinguishable by GRACE.