scholarly journals Predictions of acoustic signals from explosions above and below the ocean surface: source region calculations

1996 ◽  
Author(s):  
D.B. Clarke ◽  
A. Piacsek ◽  
J.W. White
Keyword(s):  
Source Region ◽  
Ocean Surface ◽  
Acoustic Signals ◽  
Surface Source

scholarly journals Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer?

2021 ◽  
Author(s):  
Leigh Crilley ◽  
Louisa Kramer ◽  
Francis Pope ◽  
Chris Reed ◽  
James Lee ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrous Acid ◽  
Marine Boundary Layer ◽  
Ocean Surface ◽  
Cape Verde ◽  
Formation Mechanisms ◽  
Oh Radicals ◽  
Surface Source ◽  
Global Impacts ◽  
Quantitative Understanding

Abstract. Nitrous acid, HONO, is a key net photolytic precursor to OH radicals in the atmospheric boundary later. As OH is the dominant atmospheric oxidant, driving the removal of many primary pollutants and the formation of secondary species, a quantitative understanding of HONO sources is important to predict atmospheric oxidising capacity. While a number of HONO formation mechanisms have been identified, recent work has ascribed significant importance to the dark, ocean-surface mediated conversion of NO2 to HONO in the coastal marine boundary layer. In order to evaluate the role of this mechanism, here we analyse measurements of HONO and related species obtained at two contrasting coastal locations – Cape Verde (Atlantic Ocean), representative of the clean remote tropical marine boundary layer, and Weybourne (United Kingdom), representative of semi-polluted Northern European coastal waters. As expected, higher average concentrations of HONO (70 ppt) were observed in marine air for the more anthropogenically influenced Weybourne location compared to Cape Verde (HONO < 5 ppt). At both sites, the approximately constant HONO/NO2 ratio at night pointed to a low importance for the dark ocean-surface mediated conversion of NO2 into HONO, whereas the midday maximum in the HONO/NO2 ratios indicated significant contributions from photo-enhanced HONO formation mechanisms (or other sources). We obtained an upper limit to the rate coefficient of dark ocean-surface HONO-to-NO2 conversion of CHONO = 0.0011 ppb hr−1 from the Cape Verde observations; this is a factor of 5 lower than the slowest rate reported previously. These results point to significant geographical variation in the predominant HONO formation mechanisms in marine environments and indicate that caution is required when extrapolating the importance of such mechanisms from individual study locations to assess regional and/or global impacts on oxidising capacity. As a significant fraction of atmospheric processing occurs in the marine boundary layer, particularly in the tropics, better constraint of the possible ocean surface source of HONO is important for a quantitative understanding of chemical processing of primary trace gases in the global atmospheric boundary layer and associated impacts upon air pollution and climate.

Temporal coherence and time spread of ocean surface scattered high‐frequency acoustic signals

2001 ◽  
Vol 110 (5) ◽  
pp. 2635-2635
Author(s):  
Steven Lutz ◽  
David Bradley ◽  
R. L. Culver ◽  
Joe Keranen ◽  
Jon Reeves
Keyword(s):  
High Frequency ◽  
Ocean Surface ◽  
Acoustic Signals ◽  
Temporal Coherence ◽  
Time Spread

p-Δ curves for a point source lying on a boundary

1977 ◽  
Vol 67 (6) ◽  
pp. 1521-1527
Author(s):  
George A. McMechan
Keyword(s):  
Point Source ◽  
Ocean Surface ◽  
Ocean Bottom ◽  
Surface Source

abstract A point source located at a boundary is an approximation to the physical configuration of an earthquake or an explosion at the ocean bottom. The p-Δ curves that correspond to arrivals from such a source, as observed at the ocean surface and at the ocean bottom, can be constructed by geometrical manipulations of the surface source to surface receiver p-Δ curve. p-Δ curves for multiply reflected arrivals can also be similarly constructed.

Arbitrary source and receiver positioning in finite‐difference schemes using Kaiser windowed sinc functions

Geophysics ◽  
2002 ◽  
Vol 67 (1) ◽  
pp. 156-165 ◽  
Author(s):  
Graham. J. Hicks
Keyword(s):  
Free Surface ◽  
Finite Difference ◽  
Finite Difference Methods ◽  
Source Region ◽  
Seismic Source ◽  
Point Sources ◽  
Finite Difference Schemes ◽  
Surface Source ◽  
Body Forces ◽  
Sinc Functions

In finite‐difference methods a seismic source can be implemented using either initial wavefield values or body forces. However, body forces can only be specified at finite‐difference nodes, and, if using initial values, a source cannot be located close to a reflecting boundary or interface in the model. Hence, difficulties can exist with these schemes when the region surrounding a source is heterogeneous or when a source either is positioned between nodes or is arbitrarily close to a free surface. A completely general solution to these problems can be obtained by using Kaiser windowed sinc functions to define a small region around the true source location that contains several nodal body forces. Both monopole and dipole point sources can be defined, enabling many source types to be implemented in either acoustic or elastic media. Such a function can also be used to arbitrarily locate receivers. If the number of finite‐difference nodes per wavelength is four or more (and with a source region half‐width of only four nodes) this scheme results in insignificant phase errors and in amplitude errors of no more than 0.1%. Numerical examples for sources located less than one node from either a free surface or an image source demonstrate that the scheme can be used successfully for any surface‐source or multisource configuration.

Scintillation index of ocean surface forward scattered HF acoustic signals

2004 ◽  
Vol 116 (4) ◽  
pp. 2576-2576
Author(s):  
Benjamin Cotté ◽  
David Bradley ◽  
R. Lee Culver
Keyword(s):  
Ocean Surface ◽  
Acoustic Signals ◽  
Scintillation Index
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