DETERMINATION OF CORRELATION BETWEEN SURFACE CONDITIONS AND PRESSURE WAVES AT SEA FLOOR

Wind and sea-state data are tabulated from USCG weather logs for the Brenton Reed Lightship and the Beavertail Point Lighthouse Station. To supplement this data, wave height and frequency data were measured by pressure changes a t the sea bottom from the Brenton Reed Lightship. The general procedure comprised dropping the hydrophone over the side to the bottom while leaving 15 to 20 ft of slack cable. The pressure variations were recorded for 20-min periods. The runs included 15-min sections with the hydrophone hanging 80 ft below the lightship about 10 ft off the bottom. The quantitative rule of these measurements was limited by the variation in the response of the ship. Regular wind and sea-condition estimates were made at 4-hr intervals aboard the lightship. A correlation of pressure and weather data indicated that sudden winds often result in high sea estimates whichare not observed at the bottom. As a typical storm came up, the bottom pressure variations lagged behind the surface estimates until the swell built up. These variations then continued long after the surface estimates indicated a decrease in wave action. A nummerical relationship between observed surface conditions and bottoms pressure variations was not possible because of weaknesses in the surface sea observations and the lack of suffiicient data.