Rapid Assessment of the Coastal Ocean Environment
205
when for simplicity only ASW, MW and AW are mentioned. Environmental conditions that favor the aggressor must be known to the defender and vice versa.
In an ASW scenario, the structure of the sound velocity field and its variability
are most important. Sound radiated or reflected by a subsurface structure is nearly
the only means for the detection of a submerged submarine. Under favorable conditions, sound can reliably be detected after thousands of kilometers. an the other
hand, the noise produced by a modem coastal submarine often drops below the
ambient noise level after only a couple ofkilometers, and a sonar echo from its hulI
may not exceed the reverberation from the sea surface or bottom. The non-linearity
of the relation between the depth dependent sound velocity and the detection range
does not allow for a simple statement about the required accuracy of a modeled
sound velocity field. An exemplary critical parameter is the sign of the sound
velocity gradient in the upper layer.
Acoustical methods are also used for mine detection. Because of the limited
range of detection systems, the necessary information on the sound velocity structure is fairly easily obtained by standard tools. In mine warfare, littoral ocean currents and their prediction play a dominant role. an a sandy bottom in the presence
of a sufficiently strong current, mines are buried by scouring. Mine divers are limited by a maximum current strength that obstructs swimming, and by a sediment
load that reduces visibility.
Amphibious operations depend most critically on surf conditions. Together with
the information on approaching deep water wave fields, accurate bathymetry is
required for surfpredictions. Near shore bathymetry can be modified by relocation
of sand in the currents that are generated by a storm. REA should provide an update
on coastal bathymetry, either by direct inspection or by calculation of the sand
transport in a numerical model.
In a military REA operation, potential data sources reach from public databases
over results from dedicated survey units down to sporadic measurements from
navy ships. The information is merged at a data fusion center and made available
for assimilation into models and for REA product generation (Sellschopp, 1998).
Oceanographic advisors and naval operations planners have environmental support systems and tactical decis ion aids at hand, tbat use environmental information
for the benefit ofthe military task. Without REA, these tools have to rely on climatology or single measurements extrapolated over an area. REA for the first time
offers the opportunity to use realistic physical fields in coupled tactical decision
making models.
11.3.3 Fisheries and other applications
Advanced contemporary fisheries operations and management provides another
example of environmental forecast fields coupled to strategic and tactical decision
making models. Both govemmental regulation of fisheries and commercial fishing
are involved and subjective models are in the process ofbeing augmented by quantitative numerical models. Fish spawning, larval survival and metamorphosis to
adults (recruitment) affect inter-annual and longer variations in fishing stocks, and
205
when for simplicity only ASW, MW and AW are mentioned. Environmental conditions that favor the aggressor must be known to the defender and vice versa.
In an ASW scenario, the structure of the sound velocity field and its variability
are most important. Sound radiated or reflected by a subsurface structure is nearly
the only means for the detection of a submerged submarine. Under favorable conditions, sound can reliably be detected after thousands of kilometers. an the other
hand, the noise produced by a modem coastal submarine often drops below the
ambient noise level after only a couple ofkilometers, and a sonar echo from its hulI
may not exceed the reverberation from the sea surface or bottom. The non-linearity
of the relation between the depth dependent sound velocity and the detection range
does not allow for a simple statement about the required accuracy of a modeled
sound velocity field. An exemplary critical parameter is the sign of the sound
velocity gradient in the upper layer.
Acoustical methods are also used for mine detection. Because of the limited
range of detection systems, the necessary information on the sound velocity structure is fairly easily obtained by standard tools. In mine warfare, littoral ocean currents and their prediction play a dominant role. an a sandy bottom in the presence
of a sufficiently strong current, mines are buried by scouring. Mine divers are limited by a maximum current strength that obstructs swimming, and by a sediment
load that reduces visibility.
Amphibious operations depend most critically on surf conditions. Together with
the information on approaching deep water wave fields, accurate bathymetry is
required for surfpredictions. Near shore bathymetry can be modified by relocation
of sand in the currents that are generated by a storm. REA should provide an update
on coastal bathymetry, either by direct inspection or by calculation of the sand
transport in a numerical model.
In a military REA operation, potential data sources reach from public databases
over results from dedicated survey units down to sporadic measurements from
navy ships. The information is merged at a data fusion center and made available
for assimilation into models and for REA product generation (Sellschopp, 1998).
Oceanographic advisors and naval operations planners have environmental support systems and tactical decis ion aids at hand, tbat use environmental information
for the benefit ofthe military task. Without REA, these tools have to rely on climatology or single measurements extrapolated over an area. REA for the first time
offers the opportunity to use realistic physical fields in coupled tactical decision
making models.
11.3.3 Fisheries and other applications
Advanced contemporary fisheries operations and management provides another
example of environmental forecast fields coupled to strategic and tactical decision
making models. Both govemmental regulation of fisheries and commercial fishing
are involved and subjective models are in the process ofbeing augmented by quantitative numerical models. Fish spawning, larval survival and metamorphosis to
adults (recruitment) affect inter-annual and longer variations in fishing stocks, and