Research On Data Processing Method Of Expendable Profiler

The Expendable Bathythermograph（XBT）and the Expendable ConductivityTemperature-Depth Profiler（XCTD）are important instruments for observing the ocean temperature/depth profile by navigation.Data quality is the key to ensuring its entry into operation systems.Internationally,a variety of effective data processing and calibration schemes have been proposed for different types of disposable profile measuring instruments produced by many companies.Although domestic XBT/XCTD instruments have stepped into quantitative production and have been put into application in ocean surveys,the research on data quality control and correction is extremely lacking,resulting in a blank in research on on-site measurement data processing and correction schemes for XBT/XCTD instruments in my country.Therefore,it has important application value and development significance to carry out research on observation data processing of domestic XBT/XCTD instruments,propose data correction schemes,and apply them.In this paper,the field observation data of domestic LMT XTD-800 and LMT XCTD-1000 probes in the Indian Ocean are studied and analyzed,and the XTD/XCTD error analysis is carried out with the CTD observation data of seabirds（SBE 911plus）at the same site as the benchmark.And its data correction scheme design.This paper proposes a complete data correction scheme for this type of instrument,proposes and constructs the Fall Rate Equation（FRE）for different types of instruments,and obtains more accurate correction results in the actual measurement data.The main research results of this paper are as follows:（1）In view of the current situation of insufficient accuracy of measurement data and lack of correction scheme for domestic abandoned instruments: through the analysis of the design method of XTD/XCTD instruments and the environment in which they are placed,the instantaneous response of water surface,depth deviation and effects of pure temperature deviation.The specific correction scheme is to filter and deal with abnormal values such as burr and high-frequency noise through data quality control standards,and correct the response delay of pressure sensor and temperature sensor.The calibration results of two types of XTD/XCTD arrays processed by the above calibration scheme show that: the temperature rms error of the LMT XTD-800 probe is reduced by 0.02°C,and the accuracy is increased by 9.5%;the temperature root mean square error of the XCTD-1000 probe is reduced by 0.07°C,the accuracy is improved by 15.6%.At the same time,the analysis of the correction data shows that the response delay of the XTD/XCTD sensor（depth migration problem）is the main reason for the temperature deviation,which provides a research direction for improving the data correction scheme in the next step.（2）In view of the problems of insufficient depth measurement accuracy of domestic expendable instruments and lack of study of FRE equations: construct and determine the LMT XCTD-1000 FRE parameter equation,and reconstruct the depth data on the basis of this FRE equation to achieve depth data correction.At the same time,a temperature gradient correction method is introduced to rematch the depth and temperature data.The final data correction results show that: through the FRE correction method,the temperature data RMSE is reduced by 0.14°C,and the overall temperature data RMSE is increased by 31.1%.Compared with the measurement depth correction method,the data RMSE is improved by 18.4%,which proves that the correction method based on the FRE equation is more effective and widely applicable.Internationally,XBT/XCTD probes mostly use the FRE equation to calculate the depth.Finally,this paper further discusses the future development trend of the current XBT/XCTD instrument.