There are eight vessels carrying automatic weather stations (AWS) that participate in the Australian Volunteer Observing Fleet (AVOF) program. Their routes include the Southern Ocean, coastal Australia, Bass Strait, North Pacific Ocean and the Tasman Sea. As part of the IMOS SOOP SST Sensors Sub-Facility, operated by the Bureau of Meteorology (Bureau), these AVOF vessels will be instrumented with hull-mounted temperature sensors (Sea Bird SBE 48), supplying high-quality bulk SST observations every one to three hours. There are also three passenger ferries taking SST measurements for CSIRO Marine and Atmospheric Research (Rottnest Island Ferry), the Australian Institute of Marine Science (AIMS) (Whitsunday Island to Hook Reef and Gladstone to Heron Island ferries in the Great Barrier Reef). In addition, there are near real-time SST data streams available from two Australian research vessels (RV Southern Surveyor and RSV Aurora Australis). In total, thirteen vessels by 2010 will contribute near real-time data to IMOS. All SST data are quality assured, placed in real-time on the Global Telecommunications System (GTS) and fed into the Bureau’s near real-time satellite SST data validation system and operational regional and global SST analyses. The QC’d SST data are also available in netCDF format via the IMOS data portal.
Further information relating to the call signs of the 14 vessels currently collecting IMOS SST data and the information about the sensors and dates can be found here.
Quality Control and Validation
The IMOS ship SST quality control (QC) procedure is a fully automated process, and is based on the system developed by the Center for Ocean-Atmospheric Prediction Studies (COAPS), Florida State University, for the Shipboard Automated Meteorological and Oceanographic System Initiative (SAMOS), with small differences due to varying IMOS/Bureau requirements. The QC system flags data that fail to pass the QC tests, in order of application. Once any datum’s flag is changed, it will not be altered further by any subsequent test.
In order to assess the accuracy of the largest of the initial IMOS ship SST datasets, the QC’d SBE 3 SST observations from the RV Southern Surveyor were compared against nighttime SST observations from the highly accurate Advanced Along Track Scanning Radiometer (AATSR) on the EnviSat polar-orbiting satellite for the period 1 March to 31 August 2008. The same night-time, AATSR subskin SST observations were compared with collocated, night-time, subskin SST observations from drifting and moored buoys over a similar region and six month period. The results of the three-way comparison indicated that the RV Southern Surveyor SBE 3 SST observations were an average 0.1°C warmer than buoy SSTs, and the SBE 3 SSTs exhibited 0.1°C lower standard deviation error than buoys when compared with AATSR SSTs. A similar study of the SBE 48 SST from MV Spirit of Tasmania II showed that over the period 10 December 2008 to 29 April 2009 the ship SST measurements were an average 0.14°C warmer than the AATSR subskin SSTs with a standard deviation of 0.30°C. The AATSR subskin SSTs over the same period were 0.02°C cooler than night-time buoy SST with a standard deviation of 0.38°C. Both the RV Southern Surveyor and MV Spirit of Tasmania II SST data streams should therefore prove very useful for validating/calibrating satellite SST.