ボトムトラッキングを用いた簡素なLADCPデータ処理方法

摘要

In LADCP (Lowered Acoustic Doppler Current Profiler) observations an unique data processing of followmg'procedures is examined. First, every relative velocity profile obtained with a fixed time interval in a down cast is transformed into an absolute velocity profile by adding the horizontal ADCP drift velocity at each time. Next, they are averaged for every depth and consequently a full absolute velocity profile is obtained. Here, the horizontal ADCP drift velocity at each time is estimated from the mean difference between the relative velocity profile at the time and the absolute velocity profiles at the adjoining times. For a starting point of the chain of process, absolute velocity profiles obtained by ADCP bottom tracking near a sea bottom are used. For accuracy evaluation, rms differences between the LADCP data and vessel-mounted ADCP data obtained in five observations are calculated. As a result, the rms differences classified by depth layer (36-500 m) and by observation are about 15 cm/sec in common.%LADCPデータの処理において，等時間間隔で得らrnれた個々の相対流速プロファイルを，各時刻についてrn推定したADCP水平移動速度を加算することによりrn絶対流速化し，これらを単位深度毎に平均して一つrnの流速プロファイルを得るという独自の方法を採用しrnた。その際，ADCPのボトムトラッキングデータをrn使用した。得られたデータと船底ADCPデータとのrn差のrms値は，各深度問および各調査航海間で違いrnは見られず，いずれも15cm/sec程度であった。