Remote Sensing of Antarctic Atmospheric Water Vapour using Ground-Based GPS Meteorology

Atmospheric precipitable water vapour (PWV) is one of the key components in determining and predicting the global climate system. Accurate quantification and interpretation of their physical characters using sounding technologies are quite difficult, especially in the Antarctic environment due to difficulties of the remote location and maintenance cost. This paper presents a method for deriving atmospheric PWV from ground-based GPS sensing technique. Methods for calculating the Zenith Tropospheric Delay (ZTD), Zenith Hydrostatic Delay (ZHD), Zenith Wet Delay (ZWD) and PWV are given. The Modified Hopfield model with an improvement is used to calculate ZTD, the Saastamoinen model is used to calculate ZHD and the Niell hydrostatic mapping function is used to map the ZTD to the individual satellite view. Scott Base (SBA), Casey (CAS1) and Syowa (SYOG) stations in Antarctica were taken as the observation sites. For the analysis, both GPS and surface meteorological (MET) data over the period of 2003 are presented. Before calculating the PWV, we firstly validate the ZTD determination and compared with the ZTD reference estimated from Center for Orbit Determination in Europe (CODE) Analysis Center. After that ZWD are converted into PWV using surface temperature measured at the site. Good results are achieved for ZTD validation at all stations. From statistical results found that the PWV content were below 10 mm (on average), which are all within 1~2 mm accuracy and showed that climate changes could be monitored through trends in the water vapour time series. Further work planned is to improve global climate model through quantifications, linkages, similarity or differences of either atmospheric processes between Antarctic environment and the equatorial environment.