Some of the Pathfinder datasets have been `corrected' for atmospheric loading. This is useful in many applications when the effects of atmospheric loading are not of interest, for example in the estimation of surface geostrophic currents. This loading `correction' is done by use of a simple, isostatic, inverted barometer assumption (e.g., A Gill, Atmosphere-Ocean Dynamics, Academic, 1982):
where P is the atmospheric surface pressure in millibars and 1013.3 is the global mean atmospheric pressure. In our data processing, these surface pressures are consistent with the ones used for the dry-troposphere correction. For TOPEX/POSEIDON, Geosat, ERS-2 and ERS-1 the pressures used are the operational products of the European Centre for Medium-range Weather Forecasting (ECMWF).
EXAMPLE:
This plot shows the mean inverted barometer correction during
cycle 2 of the ERS-1 Phase C exact repeat mission, i.e. during the 35-day
interval starting 19 May 1992.
