Optical Analysis for the 1971 ARPA Tower Experiment
NAVAL RESEARCH LAB WASHINGTON DC
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During the months of September and October 1971, the Naval Research Laboratory performed optical measurements at the Naval Undersea Research and Development Center tower off Mission Bay near San Diego, California. The optical measurements consisted of oblique photographs and wide-angle photography from which the ocean spectrum was analyzed as a function of time using the Sea Photo Analysis SPA technique. In conjunction with measurements being made simultaneously by other investigators, an attempt was made to experimentally determine the interaction of internal waves and wind-driven surface waves. This report discusses the results of the optical analysis of the sea photographs taken at 15-s intervals. The results show temporal variations of the spectral amplitude in the range of wavelengths from about 3 cm to 1 m. These temporal variations exhibit changes as large as 15 dB on occasion. Because of the superposition of many effects, such as tides, magnitude and direction variations of the wind, internal-wave amplitude, contamination no unique signature was deduced for the interaction of internal and surface waves. There is evidence for a mild frequency dependence of the interaction.
- Physical and Dynamic Oceanography