NICOP - Acoustic Mode Variability during the Philippine Sea Deep WaterExperiments (2009-2011)
Abstract
During the Philippine Sea EXperiment (PsiEX) in 2009-2011, six acoustic sources transmitted broadband signals to a mode resolving ve"rtical line array. The entire experiment consisted of two separate parts. The first leg of the experiment (2009-2010) was a m"onth long pilot study that consisted of a single source transmitting to a 25 element hydrophone array, at a distance of 185 km."" The second was a bigger experiment that consisted of six different sources around a Distributed Vertical Line Array (DVLA), t"hat consisted of more than 100 hydrophones. The sources were located in a hexagonal configuration and at different ranges from 129 km to 450 km. The transmission frequencies were as low as 140 Hz to as high as 325 Hz. While earlier deep water experiments conta"ined transmissions along a single path, the Philippine Sea exercise contained transmissions along multiple paths across a 250x250 km""2 area. The PsiEx environment was oceanographically dynamic, with internal tides and waves. The oceanographic variations cause acou"stic scattering. The observations during the experiment are hence an opportunity to observe acoustic scattering across a two dimensional area in an oceanographically dynamic region.This project will use the observations to answer two important questions. The first is to test the accuracy of wave propagation through random media models to predict acoustic scattering in an oceanographically dynamic region. The second is to relate the acoustic variability to low-frequency oceanographic variability in the Philippine Sea. For this the work will focus on the mode arrivals observed during both the pilot study and the larger experiment. The work will consist of two parts. The first part will develop spatial processing methods to estimate the modes from the observations recorded across the arrays. The second will focus on the estimated modes for scattering studies. The mode observations will be used to test transport" theory model predictions for mode energy and time coherence. Transport theory has been verified at 75 Hz, from an experiment in the" North Pacific. The new theory-data comparisons from the PsiEx observations will be a stringent test for transport theory at a highe"r frequencies in an oceanographically dynamic region. In addition to transport theory, this project will construct a tomography fra"mework to relate the mode observations to mesoscale changes during PsiEX.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 09, 2017
- Source ID
- N629091712084
Entities
People
- Tarun Chandrayadula
Organizations
- Indian Institute of Technology Madras
- Office of Naval Research
- United States Navy