Comparisons of global analyses and station observations of the S 2 barometric tide

Abstract

The semidiurnal atmospheric pressure oscillation—the S 2( p) tide—is deduced from two global meteorological reanalysis products: the NCEP/NCAR and GEOS-1 products. S 2 is deduced from the NCEP surface pressure product by using a special temporal interpolation devised by Van den Dool et al. The tide is deduced from the GEOS-1 product by directly analyzing six years of 3-h surface pressure fields. Two extensive collections of “ground-truth” stations are used to test the results; these are stations where the tides have been previously estimated from long time series of pressure measurements. Neither reanalysis product gives a completely adequate description of the semidiurnal tide. A new spherical harmonic expansion of S 2 is developed directly from one of the station datasets.