Cross-Evaluation of Meteorological Surface Data, and GNSS and Radiosonde derived Water Vapor, with Re-analysis Information for South Georgia Island, South Atlantic Ocean

Abstract:

As one of the most important components of the global hydrologic cycle, atmospheric water vapor shows significant variability in both space and time over a large range of scales. This variability results from the interactions of many different factors, including topography and the presence of specific atmospheric processes. One of the key regions for affecting global climatic variations lies in the sub-Antarctic zone over the Southern Ocean with its Antarctic Circumpolar Current and the associated Antarctic Convergence. There, in this cold and maritime region, lies South Georgia Island with its weather and climate being largely affected by both the dominating ocean currents and the strong eastward blowing winds in this zone. While the island forms an important outpost for various surface observations in this largely under sampled and extremely remote region, it also forms a barrier for these winds due to its high topography, which, in turn, leads to various local meteorological phenomena, such as Föhn winds.

Surface meteorological data have been available for several stations near King Edward Point (KEP) on South Georgia for much of the 20^th century. Since 2013 and 2014, Global Navigation Satellite System (GNSS) data have been available at five locations around the periphery of the island and during a few months in 2016 also radiosonde data have been collected at KEP.

This study aims at investigating the consistency between the different surface meteorological data sets such as temperature, pressure and wind direction/speed that have been collected at KEP and a nearby GNSS station. For the first time, we will compare the precipitable water vapor estimates from the GNSS stations to those from the radiosonde data. A cross-evaluation of the data sets with model values from various re-analyses will be performed to further investigate the performance of both instruments and models over this region.