Updated Results from the In Situ Calibration Site in Bass Strait, Australia

The primary Australian in situ site used for the determination of absolute altimeter bias is located in Bass Strait on the north west coast of Tasmania, Australia (40° 39’S, 145° 36’ E). This site has been used to determine absolute bias estimates since the launch of the TOPEX/Poseidon mission in 1992. More recently, a secondary site on the same TOPEX/Poseidon, Jason-1 and OSTM/Jason-2 descending pass (pass 088), has been instituted in Storm Bay (42° 18’S, 147° 39’E) to allow the investigation of the potential benefits of single-pass, multi-site absolute bias determination. The Storm Bay site has on average twice the significant wave height as that in Bass Strait, therefore enabling investigation into potential sea state effects on absolute bias determination. The Bass Strait and Storm Bay data streams are funded through Australian Integrated Marine Observing System (IMOS). In this contribution, we provide updated results from the Bass Strait site extending back to the launch of the TOPEX/Poseidon mission. We compute absolute bias estimates based on a geometric approach that involves a series of oceanographic moorings (including high accuracy pressure gauges and associated instrumentation), GPS buoys, a coastal tide gauge site and land based GPS reference stations. We conclude with preliminary results determined from the Storm Bay site where our oceanographic moorings were recently retrieved and redeployed.