Azimuthal dependent intensity fluctuations during Event-50 J. Luo, M. Badiey, and E. A. Karjadi J. Luo, M. Badiey, and E. A. Karjadi College of Marine and Earth Studies, University of College of Marine and Earth Studies, University of Delaware Delaware B. Katsnelson B. Katsnelson Voronezh University, Russia Voronezh University, Russia J. F. Lynch J. F. Lynch Woods Hole Oceanographic Institution Woods Hole Oceanographic Institution J. N. Moum J. N. Moum College of Oceanic & Atmospheric Sciences, Oregon College of Oceanic & Atmospheric Sciences, Oregon State University State University
Acknowledgements Acknowledgements We wish to thank the Office of Naval Research particularly Drs. Ellen Livingstone and Robert Headrick from 321 OA Program. Research collaborators: • J. Lynch (Woods Hole Oceanographic Institution) • B. Katsnelson (Voronezh State University) • W. Seigmann (Rensselaer Polytech Inst.) • Harry DeFerrari (RSMAS, Univ. Miami) • D. Rouseff (APL, University of Washington)
Objectives Objectives Investigate 3D effects of internal wave (IW) on the broadband acoustic propagation: Azimuthal dependency of the field due Azimuthal dependency of the field due to IW propagation. to IW propagation. Study different regimes of propagation: Study different regimes of propagation: adiabatic, horizontal refraction, mode adiabatic, horizontal refraction, mode coupling, and the transitions between coupling, and the transitions between them them
Background Background Oceanographic observations of shallow water Oceanographic observations of shallow water internal waves [Zhou et al. (1991), Rubenstein et al. (1991), Rubenstein internal waves [Zhou et al. (1991), Rubenstein (1999)]. (1991), Rubenstein (1999)]. et al. SWARM95 observation of acoustic effects SWARM95 observation of acoustic effects [Badiey et al. et al. ( 2002)]. ( 2002)]. [Badiey Theoretical explanation and hypothesis Theoretical explanation and hypothesis [Badiey et al. JASA 117(2), 2005 and JASA et al. JASA 117(2), 2005 and JASA [Badiey 122(2), 2007]. 122(2), 2007].
Experiment Waveguide Internal Signal Results Experiment Waveguide Internal Signal Results solitons solitons Zhou et al . (1991). Yellow sea Hypothesized Broadband Freq. fluct. > 20 dB α > 45 o JASA 90(4), 2042-2054 L= 28 km; D=40 m 100-1000 Hz Resonant mode Coupling Rubenstein & Brill, Washington coast N~10 cph Narrowband Temp. intens. fluct. ~ 3 dB Ocean Variability and L=18.5km; Ampl ~ 10 m f = 400 Hz Adiabatic fluctuations Acoust., 215-228 (1991). α ~ 10-15 o D=150m Rubenstein, D. (1999) Gulf of Mexico N ~ 15–20 cph Narrowband Temp. intens. fluct. ~ 2 dB IEEE J. Oceanic Eng. Mode coupling L= 30km; D=185m Ampl ~ 10 m f = 240 Hz 24(3), 346-357. α ~ 30 o Badiey, Lynch, et al. New Jersey shelf N ~ 10-15 cph Broadband 30-160 Hz Space-time int. fluct.~ 6-7dB (2002). IEEE J. Oc.Eng., L=15 km; D=70 m Ampl ~ 12 m and LFM 50-250 Hz 3D effects (horizontal v.27, N1, 117-129. α ~ 5 o refraction) Badiey, Lynch, et al. New Jersey shelf N ~ 10-15 cph Broadband 30-160 Hz Space-time int. fluct.~2-3 dB (2002). IEEE J. Oc.Eng., L=19 km; Ampl ~ 12 m and LFM 50-250 Hz Mode coupling v.27, N1, 117-129. α ~ 35-40 o D=70-100m Badiey, Katsnelson, New Jersey shelf N ~ 10-15 cph Broadband 30-160 Hz Space-time int. fluct.~ 6-7dB Lynch, et al. JASA L=15 km; D=70 m Ampl ~ 12 m 3D effects α ~ 5 o 2005 - 117(2), 613-625. Frequency dependence 2007 - 122(2), 747-760. Luo, Badiey, Katsnelson, New Jersey shelf N ~ 10-15 cph Broadband 270-330 Space-time int. fluct.~15dB Lynch, et al. JASA EL Hz L=20 km; D=70 m Ampl ~ 12 m 3D effects α ~ 3 o - 5 o 2008 - 124(3) Frequency dependence
Shark VHLA Shark VHLA Vertical linear array (VLA) 16 hydrophones 3.5 m spacing 64 m of vertical aperture • Horizontal linear array (HLA) 32 hydrophones 15 m spacing 478 m of horizontal aperture
Previous study Previous study Before & During IW event Before & During IW event
IW reconstruction IW reconstruction Radar image Radar image Interpolation using Interpolation using thermistor farm record thermistor farm record R/V Sharp radar R/V Sharp radar Thermistor farm Thermistor farm R/V Oceanous radar R/V Oceanous radar
Zone 4 Zone 5 Zone 3 Zone 2 Zone 1 Shark array
Received Signal on VLA Received Signal on VLA 21:11 -21:29 (no IW) 21:11 -21:29 (no IW) Depth = 69.75 m Depth = 47.25 m Depth = 39.75 m Depth = 28.50 m
21:41 -21:59 (angle <5 o ) o ) 21:41 -21:59 (angle <5 Depth = 69.75 m Depth = 47.25 m Depth = 39.75 m Depth = 28.50 m
22:41 -22:59 (angle = 15 o - 27 o ) o - 27 o ) 22:41 -22:59 (angle = 15 Depth = 69.75 m Depth = 47.25 m Depth = 39.75 m Depth = 28.50 m
Preliminary analysis of acoustic data Preliminary analysis of acoustic data Acoustic wave propagation mechanisms governed by the direction of acoustic track relative to the internal wave front.
Angular distribution of acoustic Angular distribution of acoustic intensity intensity Zone 5 Zone 4 Zone 3 Zone 2 Zone 1
Zone 1 Zone 2 Zone 3
Zone 4 Zone 5
time-0min-frequency-100-Hz-mode-1 time-2min-frequency-100-Hz-mode-1 1000 -0.2 1000 -0.2 -0.4 800 800 -0.4 -0.6 600 600 -0.8 400 400 -0.6 -1 200 200 antenna, m antenna, m -1.2 0 0 -0.8 -1.4 -200 -200 -1.6 -1 -400 -400 -1.8 -600 -600 -1.2 -2 -800 -800 -2.2 -1000 -1000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 track, m track, m time-2min-frequency-100-Hz-mode-2 1000 -0.2 time-0min-frequency-100-Hz-mode-2 1000 800 800 -0.4 600 600 -0.6 400 400 200 200 -0.8 antenna, m antenna, m 0 -0.8384 0 -1 -200 -200 -1.2 -400 -400 -600 -1.4 -600 -800 -800 -1.6 -1000 -1.4769 -1000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 track, m track, m
Summary Summary New data set is analyzed from a moving New data set is analyzed from a moving source to chase the IW for depicting source to chase the IW for depicting refraction refraction Appearance of the unexpected intensity Appearance of the unexpected intensity fluctuation can be related to the fluctuation can be related to the redistribution of sound field in the redistribution of sound field in the horizontal plane horizontal plane The redistribution is very sensitive to the The redistribution is very sensitive to the position of the source with respect to IW position of the source with respect to IW and the shape of IW front and the shape of IW front
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