On the accuracy of XBT temperature profiles

An evaluation of the performance of XBTs on the continental shelf off eastern Newfoundland (Northwest Atlantic) revealed that XBT temperature profiles could have significant depth offsets that vary randomly from profile to profile and are unrelated to the drop equation error identified previously. When the profiles were adjusted by applying a uniform depth offset estimated from CTD data, the depth error was significantly reduced, in most cases, to levels within the manufacturer's specifications. Thus, even at shallow water depths, where the drop equation error is not significant, XBT profiles may have significant depth offsets unless each profile is calibrated using in situ temperature data. An examination of temperature profiles from a long-term monitoring station off Newfoundland indicates that the depth offset identified in this study could be a major contributor to noise in the data.