Thirteen years of integrated precipitable water derived by GPS at Mario Zucchelli Station, Antarctica

Since 1998, the Italian Antarctic Programme is funding space geodetic activities based on the use of episodic and permanent GPS observations. Beside their exploitation in geodynamics, the data can be used to sense the atmosphere and retrieve the water vapour content and variation. The surface pressure and temperature at the GPS tracking sites are necessary to compute the precipitable water; at sites where no information is available, the values can be retrieved from a global grid model. We process the data series of the permanent GPS site TNB1 (Mario Zucchelli Station, Antarctica) from 1998 up to 2010 comparing the use of grid values to the implementation of real surface records. With both approaches, we estimate almost 70000 hourly values of precipitable water over 13 years and we find discrepancies varying between (1.8 ± 0.2) mm in summer and (3.3 ± 0.5) mm in winter. In addition, the discrepancies of the two solutions exhibit a clear seasonal dependency. We validate our results using radio soundings measurements. They agree better with the precipitable water values derived from real surface data. Nevertheless, these latter exhibit dry biases and detect the (77±21) % of the content of moisture measured by the radio soundings. Both GPS and radio sounding observations are processed adopting the most up-to-date strategies to reduce and dominate known systematic errors.