Modified Thermal Lag Correction of CTD Data from Underwater Gliders

Wang, Y.; Luo, C.; Yang, S.; Ma, W.; Niu, W., and Liu, H., 2020. Modified thermal lag correction of CTD data from underwater gliders. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 137–143. Coconut Creek (Florida), ISSN 0749-0208.A real-time data quality control process and a modified thermal lag correction procedure are proposed in this paper. The data quality control process is designed for CTD sensors (conductivity, temperature and depth) installed on Petrel gliders. A modified thermal lag correction methodology, based on the hypothesis that CTD data sampled closer in time and space would be more similar, is also put forward in this paper. Therefore, in this method, each down profile and each up profile is split into two segments. The segments with closer temporal and spatial relationships are used to calibrate each other, which is the first time the limitation of using only one profile to correct the thermal lag effect in a glider-carried CTD has been overcome. Moreover, the data obtained in sea trials with a Petrel glider and a reference SBE 911 plus CTD are used to examine the modified method and the newly designed data quality control process. The excellent alignment with the reference data and significant calibrations indicate that the CTD data were successfully corrected.