North Pacific Acoustic Laboratory - Underway CTD and SeaSoar Observations
CALIFORNIA UNIV REGENTS LA JOLLA CA SCRIPPS INST OF OCEANOGRAPHY
Pagination or Media Count:
As the limits of long-range sonar are affected by ocean variability, the overarching goal of this work is to characterize, understand, and predict sound-speed variability in the upper ocean. Sound speed is a function of the ocean state variables temperature T, salinity S, which are themselves affected by such processes as stirring, mixing and internal waves. A long-range goal is thus the inversion of acoustic data to measure these processes. Internal waves have long been considered the primary cause of acoustic energy fluctuations. However TS variations at constant density, often called spice Munk 1981, also affect sound speed. An objective of this work is to separate and quantify the effects of internal waves and spice on sound speed. The Garrett-Munk spectrum is an empirical characterization of internal waves that has withstood the test of time as a zero-order description. An equivalent statistical description of spice is an objective. Spice is strongly intermittent, and a description in terms only of power spectra may be inadequate, because it involves only the variance. An adequate characterization of spice may require higher order statistics, such as kurtosis, to describe intermittency. The mixed-layer base is especially important acoustically as the change in sound speed across it can be on the order of 10 ms in a vertical distance of 10 m. Armed with realistic statistical descriptions of internal waves, spice, and the mixedlayer base, a final objective is numerical experimentation on acoustic propagation through oceans with realistic statistical properties.
- Physical and Dynamic Oceanography
- Statistics and Probability