1e) and temperature difference (Figure 1d). These errors do not show clearly on the profiles of temperature and conductivity, but manifest on the salinity profile (Figure 1c), as spikes of psu. Such high frequency error may be caused by the irregular flow within the tag sensors, as contrary to the SBE4 cell the tag is not fitted with a pump stabilizing the inflow. Variations of the tag platform’s speed could then affect the flow velocity and turbulence within the sensor, leading to slight changes of the sensor’s response to environmental changes within the water column. Figure 1. CTD-SRDL and reference SBE CTD cast acquired on 11 June 2008 at the BOUSSOLE mooring site. (a) Temperature profiles, (b) conductivity and (c) salinity. Panels, (d), (e) and (f) display the temperature, conductivity and salinity difference (CTD minus tag) between both sensors, respectively. The thermal mass error is characterized by the strong anomaly prevalent above the thermocline within the 50 upper meters. 2.3. An independent correction scheme for salinity As a preliminary test, both the conductivity and temperature profiles of each of the 4 tags were corrected using (1) and (4) respectively, with the arbitrary values , and This test s-1. produced a significant reduction of the error (not shown) for the temperature, conductivity and salinity data of profiles such as the one displayed in Figure 1. However, correcting the temperature and conductivity separately may lead to an ambiguity in the correction of the salinity estimate. Residual discrepancies may remain due to various causes, e.g. misestimate of the coefficient values for the thermal mass correction or slight misalignment of the CTD and tag pressures, making it possible for the temperature and conductivity residual errors to compensate
1e) and temperature difference (Figure 1d). These errors do not show clearly on the profiles of temperature and conductivity, but manifest on the salinity profile (Figure 1c), as spikes of psu. Such high frequency error may be caused by the irregular flow within the tag sensors, as contrary to the SBE4 cell the tag is not fitted with a pump stabilizing the inflow. Variations of the tag platform’s speed could then affect the flow velocity and turbulence within the sensor, leading to slight changes of the sensor’s response to environmental changes within the water column. Figure 1. CTD-SRDL and reference SBE CTD cast acquired on 11 June 2008 at the BOUSSOLE mooring site. (a) Temperature profiles, (b) conductivity and (c) salinity. Panels, (d), (e) and (f) display the temperature, conductivity and salinity difference (CTD minus tag) between both sensors, respectively. The thermal mass error is characterized by the strong anomaly prevalent above the thermocline within the 50 upper meters. 2.3. An independent correction scheme for salinity As a preliminary test, both the conductivity and temperature profiles of each of the 4 tags were corrected using (1) and (4) respectively, with the arbitrary values , and s-1. This test produced a significant reduction of the error (not shown) for the temperature, conductivity and salinity data of profiles such as the one displayed in Figure 1. However, correcting the temperature and conductivity separately may lead to an ambiguity in the correction of the salinity estimate. Residual discrepancies may remain due to various causes, e.g. misestimate of the coefficient values for the thermal mass correction or slight misalignment of the CTD and tag pressures, making it possible for the temperature and conductivity residual errors to compensate