A higher-order energy-conserving parabolic equqation for range-dependent ocean depth, sound speed, and density

Collins, Michael D.; Westwood, Evan K.

doi:10.1121/1.400526

Cited by 197 publications

(73 citation statements)

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“…We need a better description of the PE modeling (Collins and Westwood, 1991). These PE results use the range dependent ocean WOA2004 (World Ocean Atlas 2004).…”

Section: D)mentioning

confidence: 99%

NPAL04 OBS data analysis part 1 : kinematics of deep seafloor arrivals

Stephen¹,

Bolmer²,

Udovydchenkov³

et al. 2008

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These notes provide supporting information for a JASA (Journal of the Acoustical Society of America) LttE (Letter to the Editor) manuscript, "Deep seafloor arrivals: A new class of arrivals in long-range ocean acoustic propagation" (Stephen et al., submitted). It addresses five issues raised by the co-authors: 1) incorrect processing for the time-compressed traces at T2300 and T3200 that appeared in an early version of the LttE (T2300, T3200 … refer to transmissions at 2300, 3200km etc from the DVLA (Deep Vertical Line Array)), 2) processing issues, including the trade-offs between coherent and incoherent stacking and corrections for the effects of moving sources and receivers and tidal currents (Doppler), 4) the distinction between "deep shadow zone arrivals", which occur below the turning points in Parabolic Equation (PE) models, and "deep seafloor arrivals", which appear dominantly on the Ocean Bottom Seismometer (OBS) but are either very weak or absent on the deepest element in the DVLA and do not coincide with turning points in the PE model (some of these OBS late arrivals occur after the finale region), 4) the role of surface-reflected bottom-reflected (SRBR) paths in explaining the late arriving energy, and 5) generally reconciling the OBS analysis with work by other North Pacific Acoustic Laboratory (NPAL) investigators and Dushaw et al (1999).

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“…We need a better description of the PE modeling (Collins and Westwood, 1991). These PE results use the range dependent ocean WOA2004 (World Ocean Atlas 2004).…”

Section: D)mentioning

confidence: 99%

NPAL04 OBS data analysis part 1 : kinematics of deep seafloor arrivals

Stephen¹,

Bolmer²,

Udovydchenkov³

et al. 2008

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“…The Range-dependent Acoustic Model (RAM) is based on the splitstep Padé solution [12,13], which allows large range steps and is the most efficient PE algorithm that has been developed. Range dependence is handled accurately by applying an energy-conservation correction [14] as the acoustic parameters vary with range. An initial condition (or starting field) is constructed using the self-starter [11], which is an accurate and efficient approach based on the PE method.…”

Section: Parabolic Equation Methods -Rammentioning

confidence: 99%

Effects of internal waves on low frequency, long range, acoustic propagation in the deep ocean

Xu¹

2007

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This thesis covers a comprehensive analysis of long-range, deep-ocean, low-frequency, sound propagation experimental results obtained from the North Pacific Ocean. The statistics of acoustic fields after propagation through internal-wave-induced sound-speed fluctuations are explored experimentally and theoretically.The thesis starts with the investigation of the North Pacific Acoustic Laboratory 98-99 data by exploring the space-time scales of ocean sound speed variability and the contributions from different frequency bands. The validity of the Garret & Munk internal-wave model is checked in the upper ocean of the eastern North Pacific. All these results impose hard bounds on the strength and characteristic scales of sound speed fluctuations one might expect in this region of the North Pacific for both internal-wave band fluctuations and mesoscale band fluctuations.The thesis then presents a detailed analysis of the low frequency, broadband sound arrivals obtained in the North Pacific Ocean. The observed acoustic variability is compared with acoustic predictions based on the weak fluctuation theory of Rytov, and direct parabolic equation Monte Carlo simulations. The comparisons show that a resonance condition exists between the local acoustic ray and the internal wave field such that only the internal-waves whose crests are parallel to the local ray path will contribute to acoustic scattering: This effect leads to an important filtering of the acoustic spectra relative to the internal-wave spectra. We believe that this is the first observational evidence for the acoustic ray and internal wave resonance.Finally, the thesis examined the evolution with distance, of the acoustic arrival pattern of the off-axis sound source transmissions in the Long-range Ocean Acoustic Propagation EXperiment. The observations of mean intensity time-fronts are compared to the deterministic ray, parabolic equation (with/without internal waves) and (one-way coupled) normal mode calculations. It is found the diffraction effect is dominant in the shorter-range transmission. In the longer range, the (internal wave) scattering effect smears the energy in both the spatial and temporal scales and thus has a dominant role in the finale region.

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“…a profuse num ber of developm ents have been carried out to improve the accuracy and efficiency of the approxim ation [2,[44][45][46][47][48][49][50][51][52][53], and to expand i t 's applicability to more realistic conditions [54][55][56][57][58][59][60][61]. T he parabolic equation was originally lim ited to narrow -angle propagation; th e energy outside the angle of propagation is neglected.…”

Section: P Arabolic E Quation M Eth O Dmentioning

confidence: 99%