Temperature Measurement Array for Internal Wave Observations

During the last six years the Marine Physical Laboratory has been engaged in a study of the internal wavefield in the upper ocean. Inasmuch as internal waves propagate horizontally, vertically, and in time, a four-dimensional (space-time) measurement was desired. To meet these requirements, a three-element temperature sensor system in an array 40 meters on a side, was created by mounting 3 booms on the R/P FLIP. Repeated temperature profiles were made from each of these booms. The system consists of temperature and depth profile sensors, winches to raise and lower the sensors, a computer to manage the data, and a central control unit. A vibrotron pressure sensor and two variable frequency thermometers are suspended from each of the booms. The first thermometer and the pressure sensor are placed at the bottom end of a 500 meter cable; a second thermometer is attached 188 meters up the cable. The cables are raised and lowered simultaneously by individual winches. Lowering the winch cable 220 meters provides sampling over a depth of 400 meters in the water column. The drop rate of the sensors is 4.5 meters/second. Vertical temperature resolution is 1 meter. Profiles are taken every two minutes by the three elements. The sensors are scanned by the computer while the elements descend. While the elements are being raised the computer is utilized for data display and initial analysis.