Effect of the atmospheric pressure on surface displacements

Atmospheric pressure variations with periods of some days and months can be considered as loading functions on the Earth's surface and can induce quasi-perio dic surface deformations. The influence of such surface displacements is calculated by performing a convolution sum between the mass loading Green's functions and the local and regional barometric pressure data (geographically distribution in a 1 degrees x 1 degrees grid system extending to more than 1000 km). The results for 5 stations in Europe show that the average values reach about 22.9-30.2 mm depending on the ocean response: the inverted or non-inverted barometer ocean model. The corresponding admittances are 0.576-0.758 mm/mbar respectively. The horizontal displacements are not negligible but always smaller. The magnitudes are about 2-3 mm for East-West component and 0.5-1.0 mm for North-South component. The results of the dependence on the lateral extension of the pressure load show that the admittance for radial displacement varies from 0.250 mm/mbar for a column load of 100 km radius to 0.539 mm/mbar for a column load of more than 1000 Km extension. It means that the main contribution of the loads comes from the horizontal distribution of the air pressure in a broad region. The time dependent effects of the atmospheric pressure are also computed with the two-coefficient correction equations provided by Rabbel & Zschau (1985) using ground pressure data in a 1.125 degrees x 1.125 degrees grid system. The computations demonstrate that the results are in good agreement with those obtained with a convolution sum. It shows that this method can provide us with a good approximation for vertical displacement caused by the deformation of the Earth.