20
G. Budillon et al.
The use of HF radar signal to characterize
the surface circulation of a sea area was first
explored by Crombie (1955) (for a review see
Lipa and Barrick 1983; Prandle 1991; Fernandez
1993), who observed that those signals were
backscattered by ocean waves of precisely half
the radar wavelength. The general working principle of these instruments is based on the
Doppler shift of the Bragg-scattering waves
propagating radially towards or away from the
radar. This yields, obviously, the necessity of utilizing at least two radar installations in order to
get a characterization of the two-dimensional
surface velocity field.
Over the last years two systems have been
developed and subsequently utilized based on
the above principles: the Coastal Ocean
Dynamics Applications Radar (CODAR, see
Barrick et al. 1977) and the Ocean Surface
Current Radar (OSCR, see Prandle 1987; Shay et
al. 1995). This latter utilizes an 85 m long, 16 or
32 element phased-array antenna, emitting a
narrow beam electronically guided over the
studied area. The CODAR antennae, on the con43.7
trary, consist of two crossed loops and a monopole, and are comparatively a very compact system. Radial velocities are retrieved from the seaecho Doppler spectra by a least squares method
(Lipa and Barrick 1983).
Drawbacks and advantages of the two systems are an obvious consequence of the above:
the OSCR implies a relatively simple signal processing technique; on the other hand, it is a voluminous system, and its installation is quite
demanding. The CODAR is a much more compact, easy to set up device, but requires heavier
data postprocessing. While until the recent past
most published results refer to OSCR measurements (Prandle and Ryder 1985; Prandle 1991;
Prandle et al. 1993; Shay et al. 1995), the refmement of data analysis techniques has lately led to
the assessment of the accuracy of CODAR systems which have been successfully employed off
the coast of British Columbia (Masson 1996) and
in Monterey Bay (Paduan and Rosenfeld 1996).
For the above reasons, a CODAR system was
selected to map surface currents in the area off
Ancona.
J
43.hL~--------------~~--~~~--~---r------~
13.2
13.4
13.6
Fig. 1. Map of the studied area.
The dots represent the 30 x 30
km radar measurement locations considered in the present
work. Contours refer to the normalized data density over the
three month period August
through October 1997
Longitude
G. Budillon et al.
The use of HF radar signal to characterize
the surface circulation of a sea area was first
explored by Crombie (1955) (for a review see
Lipa and Barrick 1983; Prandle 1991; Fernandez
1993), who observed that those signals were
backscattered by ocean waves of precisely half
the radar wavelength. The general working principle of these instruments is based on the
Doppler shift of the Bragg-scattering waves
propagating radially towards or away from the
radar. This yields, obviously, the necessity of utilizing at least two radar installations in order to
get a characterization of the two-dimensional
surface velocity field.
Over the last years two systems have been
developed and subsequently utilized based on
the above principles: the Coastal Ocean
Dynamics Applications Radar (CODAR, see
Barrick et al. 1977) and the Ocean Surface
Current Radar (OSCR, see Prandle 1987; Shay et
al. 1995). This latter utilizes an 85 m long, 16 or
32 element phased-array antenna, emitting a
narrow beam electronically guided over the
studied area. The CODAR antennae, on the con43.7
trary, consist of two crossed loops and a monopole, and are comparatively a very compact system. Radial velocities are retrieved from the seaecho Doppler spectra by a least squares method
(Lipa and Barrick 1983).
Drawbacks and advantages of the two systems are an obvious consequence of the above:
the OSCR implies a relatively simple signal processing technique; on the other hand, it is a voluminous system, and its installation is quite
demanding. The CODAR is a much more compact, easy to set up device, but requires heavier
data postprocessing. While until the recent past
most published results refer to OSCR measurements (Prandle and Ryder 1985; Prandle 1991;
Prandle et al. 1993; Shay et al. 1995), the refmement of data analysis techniques has lately led to
the assessment of the accuracy of CODAR systems which have been successfully employed off
the coast of British Columbia (Masson 1996) and
in Monterey Bay (Paduan and Rosenfeld 1996).
For the above reasons, a CODAR system was
selected to map surface currents in the area off
Ancona.
J
43.hL~--------------~~--~~~--~---r------~
13.2
13.4
13.6
Fig. 1. Map of the studied area.
The dots represent the 30 x 30
km radar measurement locations considered in the present
work. Contours refer to the normalized data density over the
three month period August
through October 1997
Longitude