STARTWAVE

STudies in Atmospheric Radiative Transfer
and Water VApour Effects

Correcting the GPS Integrated Water Vapour data for altitude differences

The GPS receivers in the Automated GPS Network of Switzerland (AGNES) are situated at altitudes between 330 and 3584 m. There is much more water vapour above the Muttenz station in the Swiss plains (330 m) than above the Jungfraujoch station on a high Alpine pass (3584 m). The plot below demonstrates the average change in IWV with altitude from observations made by the GPS stations in the AGNES network during the months of January and July.

If we plot the IWV measurements on a map we see lower water vapour amounts at high altitudes and higher amounts at low altitudes. In order to obtain information on the spatial distribution of water vapour we must first of all calculate the IWV at a standard altitude.For the Swiss Alpine region, we have chosen an altitude of 500 m.

The altitude correction for the Swiss GPS network is described in: J. Morland, C. Mätzler, Spatial interpolation of GPS integrated water vapour measurements made in a mountainous terrain, submitted to Meteorological Applications, 2005.