ALBERT

Description: Argo is the most visible and innovative new element of the sustained observing system for the open ocean. Since mid-2004 it has become the most abundant source of profile data from the ocean and that abundance will continue to increase as the array grows to its target of 3000 floats that will deliver 100,000 CTD profiles per year by 2007. Paradoxically, the existence of Argo has highlighted the importance of research ship-based CTD observations. Argo floats are expendable, consequently there is no opportunity to do laboratory calibrations to check sensor drift. A method has been devised to estimate sensor drift by making comparisons with nearby (in space and time) CTD profiles collected by research ships and by comparing new and old floats. This method is described in : Wong, A.P.S., Johnson, G.C. Owens, W.B., 2003. Delayed-Mode Calibration of Autonomous CTD Profiling Float Salinity Data by Theta-S Climatology. Journal of Atmospheric and Oceanic Technology, 20, 308-318. Böhme, Lars and Uwe Send, 2005: Objective analyses of hydrographic data for referencing profiling float salinities in highly variable environments. Deep-Sea Research II, 52/3-4, 651-664. The estimation of float sensor drift requires a regular supply of ship-board CTD profiles to depths of at least 1000m in water depths of 2000m or more. Unfortunately, most of these data are not easily available to Argo community, and those that are available arrive after unacceptably long delays. IODE & the NODCs are asked to assist in making these data more easily and rapidly available to Argo. Rather schematically, one can distinguish data that are used in delayed mode (the study of ocean processes, surveys to assess low-frequency variability, building up climatology), from those used in real time (or near real time) for assimilation into ocean circulation models for operational purposes. The calibration of Argo profiles falls in both categories: validation as soon as possible after deployment, and delayed mode quality control.

Description: Supported by IOC/IODE

Description: Document available in English

Description: Observing system