Doppler Sonar and Profiling CTD Observations of the Interrelationship between Large and Small Scale Internal Waves

摘要

At the Marine Physical Laboratory, two instrument systems have been developed for the purpose of bridging the gap between large and small scales. A profiling CTD was constructed in the early 1970's. This senses the vertical displacements in the sea by tracking the depths of isothermal okr isopycnal surfaces. Vertical scales of 1 m to 400 m are resolved by the system. In the late 1970's Doppler sonar technology was developed. Sonars provide the capability to profile in directions other than vertical. Ranges in excess of 1 km can be sampled. However, the sonar range resolution is worse than the CTD, being approximately 20 m. This report will document the view of the upper ocean as seen by the Doppler sonar and the CTD systems. Data from the May 1980 operation, as well as from earlier FLIP operations will be presented. Examples of depth-time series and power spectra will be presented for both systems. Combined wavenumber-frequency spectra will be used to demonstrate the relative amplitudes of the large scale-low frequency versus the small scale high frequency signals. Emphasis will be placed on the types of motions which are missed as well as measured by these two systems, as well as on disagreements in the measurements obtained.