Displacements of the Earth's surface due to atmospheric loading: Effects on Gravity and Baseline Measurements

Atmospheric mass loads and deforms the Earth's crust. By performing a convolution sum between daily global barometric pressure data and mass loading Green's functions, we estimate the time dependent effects of atmospheric loading, including those associated with short-term synoptic storms, on surface point positioning measurements and surface gravity observations. We calculate the response of both an oceanless Earth and an Earth with an inverted barometer ocean. Peak to peak vertical displacements are frequently 15-20 mm with accompanying gravity perturbations of 3-6 microgal. Baseline changes can be as large as 20 mm or more. The perturbations are largest at higher latitudes and during winter months. These amplitudes are consistent with the results f Rabbel and Zschau (1985) who modeled synoptic pressure disturbances as Gaussian functions of radius about a central point. Deformation can be adequately computes using real pressure data from points within about 1000 km of the station. Knowledge of local pressure alone, is not sufficient. Rabbel and Zschau's hypothesized corrections for these displacements, which use local pressure and regionally averaged pressure, prove accurate at points well inland but are, in general, inadequate within a few hundred kilometers of the coast.