Assessing the quality of sea surface temperature observations from drifting buoys and ships on a platform-by-platform basis

This study investigates how the quality of sea surface temperature (SST) observations made by drifting buoys (drifters) and ships for 1996-2010 can be improved through retrospective quality control (QC) against a reference field. The observations used are a blend of delayed mode data taken from the International Comprehensive Ocean-Atmosphere Data Set (versions 2.0 and 2.5) and real time data obtained from the Global Telecommunication System. A comparison of drifter and ship measurements on a platform-by-platform basis to high-quality SST estimates from the Along track scanning radiometer Reprocessing for Climate (ARC) project reveals drifter observations are generally of good quality but frequently suffer from gross errors, whilst ship observations are generally of worse quality and show a diverse range of measurement errors. QC procedures are developed which similarly assess drifter and ship SST observations through comparison with the Met Office Operational SST and Sea Ice Analysis (OSTIA). These procedures make use of seasonal background error variance estimates now available for OSTIA. Drifter observations displaying some commonly observed gross errors are flagged and ship callsigns whose observations are deemed unreliable are blacklisted. Validation of the QC outcomes against ARC and Argo demonstrates that this retrospective QC improves the quality of drifter and ship observations, though some limitations are discussed.