Computation of the atmospheric gravity correction in New Zealand

Abstract

The proper treatment and the accurate modelling of atmospheric gravity correction and other environmental effects on gravity measurements are indispensable in precise gravimetric applications such as detailed gravity surveys, micro-gravimetry and other geophysical studies which require high accuracy. In this study we apply a novel approach to compute the atmospheric gravity correction. This approach is based on an analytical integration which utilises a newly derived closed expression for the gravitational effect of a truncated spherical shell having a density varying in the radial direction. The atmospheric gravity correction is evaluated as the atmospheric component of the normal gravity at the computation point from which the gravitational effect of the topography-bounded atmosphere is subtracted. The gravitational effect of the topography-bounded atmosphere is computed by volumetric integration over atmospheric masses, considering topography as the lower atmospheric bound. This new approach is applied to compute the atmospheric gravity correction in New Zealand. The numerical results reveal that the gravitational effect of the topography-bounded atmosphere varies from (0.009 mGal (offshore) up to 0.203 mGal (in the region of Mt Cook). The corresponding values of the atmospheric gravity correction vary between 0.671 and 0.884 mGal. We also demonstrate that the errors in computed values of the atmospheric gravity correction exceed Â0.1 mGal when disregarding topography as the lower atmospheric bound.