Acoustic Propagation Uncertainty in the Shallow East China Sea

Acoustic transmission loss (TL) and supporting ocean environmental data collected during the Asian Seas International Acoustics Experiment (ASIAEX) on June 3, 2001, in the East China Sea (ECS), in a water depth of approximately 100 m are presented. Objectives of the data analysis are to explore the stochastic nature of TL in terms of the mean (mu _TL) and the fluctuations around the mean (as described by the standard deviation (sigma_TL) and higher order statistics). In particular, we conjecture that mu_TL robustly reflects the macrostate of the ocean, including the bottom, whereas uncertainties in TL as measured by sigma_TL are related to the microstate of the ocean, again including the bottom. Comparisons are made to TL data at a similar location, 200 km from the ASIAEX site, in waters of the same depth, by the Harsh Environment Program in September 1997. The TL is shown to be approximately horizontally isotropic with exception to a discrete anisotropic feature likely caused by internal waves. Various mechanisms of uncertainty are discussed to describe the microstate. These were not sufficiently resolved to identify the primary cause of variability