Atmospheric mass flow reduction for terrestrial absolute gravimetry in the fennoscandian land uplift network

Temporal variations of the atmospheric density distribution induce changes in the gravitational air mass attraction at a specific observation site. Additionally, the load of the atmospheric masses deforms the Earth's crust and the sea surface. Variations in the local gravity acceleration and atmospheric pressure are known to be correlated with an admittance of about -3 nms^-2 per hPa as an average factor, which is in accordance with the IAG Resolution No. 9, 1983. A more accurate correlation factor for a gravity station is varying with time and depends on the total global mass distribution of the atmosphere. For the absolute gravimetric observations of the Fennoscandian land uplift, the atmospheric attraction effect of the local zone has been calculated with 3D atmospheric data describing different pressure levels up to a height of 50 km. To model the regional and global attraction and deformation components with Green's functions method, 2D surface atmospheric data have been used. The improved atmospheric effects have been computed for the position-dependent absolute gravity observations in Fennoscandia performed by the Institut für Erdmessung (IfE) in 2003. The objective is to ensure an air mass reduction within ±3 nms^-2 accuracy. For the 2003 campaigns, the use of atmospheric actual data has improved the reductions by about 9 nms^-2 (max. 14 nms^-2).