The Method And Its Application For Separating Tidal And Subtidal Currents From Ship-mounted ADCP Data

The theisi analyzes the objectives and significance of the current research by reviewing the development and application of ADCP and the methodological progresses for separating tidal and subtidal currents from ship-mounted ADCP data.By selecting proper knot numbers and basis function,the tidal and subtidal currents from ship-mounted ADCP data recored in the Songyu-Gulangyu transect and the Xiamen-Gulangyu transect are thesis separated with "Candela's method" and the tidal and subtidal currents computed.At the same time,the tidal and subtidal currents are computed with the traditional harmonic analysis method for verifying the applicability of Candela's method in the analysis of data from repeated ship-mounted ADCP measurement in a transect.The analysis of the knot numbers and the basis function indicates that the best knot number is K=9 and the optimal basis function is Green Function for Candela's method applied in the Songyu-Gulangyu and the Xiamen-Gulangyu transects.It is prelimarily concluded in case of insuffiicent data at individual computation points,Candela's method can still be used in separating tidal and subtidal currents when the data are sufficient at other computation points.By using the best knot numbers(K=9) and the optimal basis function (Green Function),we carried on data selection analysis and found when data reduces to half of the completation data(selecting data every one come-and-go),the results from Candela's method still fits with that from the analysis of the complete set of data.The results from the analysis of the response of Candela's method to the change of computation point numbers by increasing computation point numbers indicate very small computation errors.The tidal flux at the Songyu-Gulangyu and Xiamen-Gulangyu transects were calculated from ADCP field measurements.By making repeated measurements with ship-mounted ADCP at one transect,one can measure the flow velocity,direction and water depth at neighboring points several meters apart and at every 0.5 meter.Moreover,as several come-and-go measurements may be done in one cruise,the resolutions of flow flux are greatly improved both at space and time.In brief,the method for separating tidal and subtidal currents from ship-mounted ADCP discussed in the thesis is feasible to separate tidal and subtidal currents from data of ship-mounted ADCP repetitively measured in the Songyu-Gulangyu and Xiamen-Gulangyu transects in the Xiamen Bay.