IN-SITU OBSERVATIONS
203
The geostrophic transport monitoring is suitable for timeseries of
transports over entire sections. These maybe confined currents (passages),
wide boundary currents, or meridional flows across entire ocean basins. In a
German CLIVAR application (MOVE project), this was carried out
successfully over a 1000km long section.
Strengths and weaknesses:
Acoustic tomography is an expensive technique requiring highly
specialized teams and equipment. The niche in providing large-scale
integrals has become smaller with the advent of ARGO, but the strengths
remain full depth coverage and occupation of specific sections of interest.
Both tomography and geostrophic integral techniques require specific
geometry and bathymetry, thus cannot be used anywhere. However, they are
remote sensing approaches, providing integral information about ocean
regions without the need to deploy instruments everywhere.
Further readings: Kanzow et al (2005), Dushaw et al (2001).
2.7 Coastal radars
Description:
Radar installations with typically 50-150km range are able to sense the
surface currents in the vicinity of coasts, by analyzing the doppler shift from
surface waves which Bragg-scatter the radar signal. Each piece of ocean
surface to be sensed needs to be covered by two separate radars. The
variables that can be extracted are the very near-surface current vectors, and
as a second-order quantity, the wave height. The spatial resolution is 2-3km,
and the time resolution typically 1 hour. Shorter-range systems also exist.
Application:
For operational applications like ship routing, prediction of pollutant
transport, harmful algal blooms, etc, this is is a method of increasing
interest. To date, most installations are only in select locations of specific
interest. However, some countries are starting to set up radar networks along
entire coastlines. These would contribute to monitoring systems of coastal or
near-shore ocean processes.
Strengths and weaknesses:
An advantage of radars is that they are entirely land-based and have
useful spatial and temporal resolution. However, they coverage is limited to
near-coast, they require elevated terrain for the installations, and can only
sense currents at the surface.
Further readings: Essen et al (2000), EuroROSE website.
203
The geostrophic transport monitoring is suitable for timeseries of
transports over entire sections. These maybe confined currents (passages),
wide boundary currents, or meridional flows across entire ocean basins. In a
German CLIVAR application (MOVE project), this was carried out
successfully over a 1000km long section.
Strengths and weaknesses:
Acoustic tomography is an expensive technique requiring highly
specialized teams and equipment. The niche in providing large-scale
integrals has become smaller with the advent of ARGO, but the strengths
remain full depth coverage and occupation of specific sections of interest.
Both tomography and geostrophic integral techniques require specific
geometry and bathymetry, thus cannot be used anywhere. However, they are
remote sensing approaches, providing integral information about ocean
regions without the need to deploy instruments everywhere.
Further readings: Kanzow et al (2005), Dushaw et al (2001).
2.7 Coastal radars
Description:
Radar installations with typically 50-150km range are able to sense the
surface currents in the vicinity of coasts, by analyzing the doppler shift from
surface waves which Bragg-scatter the radar signal. Each piece of ocean
surface to be sensed needs to be covered by two separate radars. The
variables that can be extracted are the very near-surface current vectors, and
as a second-order quantity, the wave height. The spatial resolution is 2-3km,
and the time resolution typically 1 hour. Shorter-range systems also exist.
Application:
For operational applications like ship routing, prediction of pollutant
transport, harmful algal blooms, etc, this is is a method of increasing
interest. To date, most installations are only in select locations of specific
interest. However, some countries are starting to set up radar networks along
entire coastlines. These would contribute to monitoring systems of coastal or
near-shore ocean processes.
Strengths and weaknesses:
An advantage of radars is that they are entirely land-based and have
useful spatial and temporal resolution. However, they coverage is limited to
near-coast, they require elevated terrain for the installations, and can only
sense currents at the surface.
Further readings: Essen et al (2000), EuroROSE website.