Chapter 7: APPLICATIONS
(Paulson and Lagerloef, 1993; Soloviev and Lukas, 1997a), which
corresponds to a few m s
-1 difference in the speed of sound.
Significant surface salinity (as well as temperature) changes have been
observed near icebergs. Lugt and Uglimchius (1964) estimated that the
sound propagating horizontally through the cool and fresh water in the
vicinity of an iceberg could refract up to about 18
o .
7.4.2 Biological scattering layers
Objects containing internal gas volumes may resonate at certain
frequencies and produce very intense scatter of sound. Thin, concentrated
layers of phytoplankton and zooplankton in the near-surface layer have
layers range from only a few tens of centimeters to a few meters in
vertical extent (Cowles et al. 1998, Hanson and Donaghay 1998). Biota in
these layers is often highly concentrated. Layers can be continuous
horizontally for at least kilometers and persistent for days to weeks, strongly
affecting the optical and acoustical properties of the water column
(Donaghay and Osborn, 1997, Rines et al., 2002).
Figure 7-9 reveals the persistence of a thin layer of zooplankton (green
solar radiation. Note that the near surface layer of intense scatter
(red regions
Under high wind speed conditions, wind-wave turbulence destroys
The frequency of the appearance of sound scattering biological layers in
the near-surface layer of the open ocean is practically unknown. In the open
ocean, these layers can supposedly appear during algae blooms. One of the
authors of this book (AVS) observed a thin layer of biota in the North
Atlantic Ocean (39
o N, 20
o W) during a calm weather period in July 1982.
This layer produced an appreciable disturbance to the electromagnetic
velocity sensor (this type of sensor is described in Chapter 3) during
measurements with a free-rising profiler. The layer was first detected at
about 20 m depth and was gradually moving towards to the ocean surface.
461
episodically been observed in the coastal ocean (Section 7.3). These thin
line, about 65 dB) over a 48-hour period. The thin layer was close to the
thermocline.During the night hours it
in Figure 7-9) is due to bubbles generated in the process of wave
breaking.
was masked by the vertical migration
of zooplankton .(Presumption is that feeding is the driving force
biological scattering layers in the near-surface layer.
for these
migrations.)morning hours when the convection is inhibited due to the
absorption of
(Paulson and Lagerloef, 1993; Soloviev and Lukas, 1997a), which
corresponds to a few m s
-1 difference in the speed of sound.
Significant surface salinity (as well as temperature) changes have been
observed near icebergs. Lugt and Uglimchius (1964) estimated that the
sound propagating horizontally through the cool and fresh water in the
vicinity of an iceberg could refract up to about 18
o .
7.4.2 Biological scattering layers
Objects containing internal gas volumes may resonate at certain
frequencies and produce very intense scatter of sound. Thin, concentrated
layers of phytoplankton and zooplankton in the near-surface layer have
layers range from only a few tens of centimeters to a few meters in
vertical extent (Cowles et al. 1998, Hanson and Donaghay 1998). Biota in
these layers is often highly concentrated. Layers can be continuous
horizontally for at least kilometers and persistent for days to weeks, strongly
affecting the optical and acoustical properties of the water column
(Donaghay and Osborn, 1997, Rines et al., 2002).
Figure 7-9 reveals the persistence of a thin layer of zooplankton (green
solar radiation. Note that the near surface layer of intense scatter
(red regions
Under high wind speed conditions, wind-wave turbulence destroys
The frequency of the appearance of sound scattering biological layers in
the near-surface layer of the open ocean is practically unknown. In the open
ocean, these layers can supposedly appear during algae blooms. One of the
authors of this book (AVS) observed a thin layer of biota in the North
Atlantic Ocean (39
o N, 20
o W) during a calm weather period in July 1982.
This layer produced an appreciable disturbance to the electromagnetic
velocity sensor (this type of sensor is described in Chapter 3) during
measurements with a free-rising profiler. The layer was first detected at
about 20 m depth and was gradually moving towards to the ocean surface.
461
episodically been observed in the coastal ocean (Section 7.3). These thin
line, about 65 dB) over a 48-hour period. The thin layer was close to the
thermocline.During the night hours it
in Figure 7-9) is due to bubbles generated in the process of wave
breaking.
was masked by the vertical migration
of zooplankton .(Presumption is that feeding is the driving force
biological scattering layers in the near-surface layer.
for these
migrations.)morning hours when the convection is inhibited due to the
absorption of