Assessment of the Jason-1 and TOPEX/Poseidon Microwave Radiometer Performance Using GPS from Offshore Sites in the North Sea

Abstract

The accuracy and drift of atmospheric path delay due to water vapor as derived from satellite microwave radiometers (MWR) is vital to altimetric measures of sea-level change. In this study a continuous time series of dual frequency GPS data from a number of offshore sites is used to examine the long term stability of the TOPEX/Poseidon radiometer and investigate initial performance of that of Jason-1. The location offshore eliminates the problems associated with land based/coastal locations where extrapolation of the GPS tropospheric correction to subsatellite points offshore are required to avoid background surface heat emissions contaminating the MWR delay measurement.

Keywords:

• GPS
• microwave radiometer stability
• zenith wet delay

Acknowledgments

The authors wish to thank the reviewers for their helpful comments and the NASA JPL group for the provision of precise orbit and clock products within the GIPSY/OASIS II software in this experiment.

Note: The sign convention in Figure 2 and Figure 4 corresponds to a positive value for GPS ZWD, which differs from Figure 3 and Figure 5 where the altimetric convention of negative tropospheric delay has been adopted to ease comparison with other investigations.

Note: Positive sign convention.