Examining the Influence of Recording System on the Pure Temperature Error in XBT Data

Abstract Expendable bathythermographs (XBTs) have been widely deployed for ocean monitoring since the late 1960s. Improving quality of XBT data is a vital task in climatology. Many factors (e.g., temperature, probe type, and manufacturing time) identified as major influences systematic bias. In addition, recording system (RS) has long suspected another factor. However, this factor not taken into account any global correction schemes, partly because its impact poorly understood. Here, based on analysis an XBT–CTD side-by-side dataset collocated reference dataset, influence RSs pure temperature error (PTE) examined. Results show clear time dependency PTE RS, with maximum values occurring 1970s. method used to convert thermistor resistance RS (using resistance–temperature equation) changed over time. These changes, together decadal changes RSs, might contribute small (10% average) dependency. improvement bias that accounts proposed. more than 70% historical are missing RS-type information. We investigate several assumptions about temporal distribution types, all scenarios lead at least ~50% reduction variation compared uncorrected data. Therefore, should be updated which would further implications climatology studies.