Fall AGU Meeting (Dec. 2002) COAST abstracts:

• Allen
  
• Bane et al.
  
• Barth et al.
  
• Carney et al.
  
• Couch et al.
  
• Cowles et al.
  
• Dale et al.
  
• Durski et al.
  
• Egbert et al.
  
• Gan et al.
  
• Hales et al.
  
• Kosro et al.
  
• Kuebel et al.
  
• Kurapov et al.
  
• Perlin et al.
  
• Pierce et al.
  
• Ruttenberg et al.
  
• Samelson
  
• Spitz et al.
  
• Wheeler
  

Abstracts should be cited as:

EOS Trans. AGU, 83 (47),
Fall Meet. Suppl.,
Abstract XXXXX-XX, 2002

OS51D-09

Tidal Currents on the Central Oregon Shelf: Models, Data, and
Assimilation

G D Egbert, L Erofeeva, and P M Kosro

Measurements of tidal currents on the central Oregon shelf
are available from several sources, including recent high
frequency (HF) coastal radar and Acoustic Doppler Profiler (ADP)
deployments, and historical current moorings.  In this paper we
use a generalized inverse (GI) approach to compare these data to,
and then assimilate them into, numerical models for the barotropic
tides.  Harmonic analysis of the data in short time windows using
a modified admittance approach reveals that tidal currents on
the Oregon shelf are highly variable in time, and can contain
significant baroclinic components. Data from the winter months,
when waters on the shelf are only weakly stratified, are found to
be most nearly barotropic and thus most reasonable for assimilation
into the shallow water equations model. The various data sources
are used in several different combinations for assimilation and
validation. Forcing the prior forward model with normal flow open
boundary conditions obtained from a regional barotropic inverse
model results in semi-diurnal barotropic currents that are consistent
(within estimated error limits) with all available data. In contrast,
diurnal currents on the shelf are very sensitive to details of
the model configuration, and are significantly improved by data
assimilation. Very similar solutions result from assimilation of
either the HF radar or ADP data sets. The high sensitivity of the
diurnal band currents can be understood dynamically in terms of
trapped shelf waves. A short (~ 85 km long) section of shelf off the
central Oregon coast is wide enough to allow first-mode barotropic
shelf waves at the sub-inertial diurnal frequencies. This results
in locally resonant large amplitude diurnal tidal currents that
are very sensitive to details in the local forcing, and hence quite
variable in time.