Amplitude in metres of the dry troposphere correction computed from the ECMWF atmospheric pressures and model during the Jason1 cycle 223. This map is drawn using the Basic Radar Altimetry Toolbox from the Jason1 GDR products. A Loess filter (value of 31) is applied to obtain a fully coloured plot. 
The dry tropospheric range correction in units of cm can be approximated by the Saastamoinen formula: ΔRdry= 0.02277Po*(1+0.0026cos2φ) where Po is the sea level pressure in Pascal and φ the latitude. Thus, the dry tropospheric range delay is proportional to sea level pressure and also depends to the latitude (φ). An sea level pressure error of 5 mbar corresponds to a range error of about 1 cm.
Since it is impossible to currently estimate the sea level pressure by spaceborne techniques, the dry troposphere correction must be obtained from meteorological models.
