Miller, A. J., H. G. Arango, A. R. Robinson, W. G. Leslie,
P.-M. Poulain and A. Warn-Varnas, 1995:
Quasigeostrophic forecasting and physical processes
of Iceland-Faroe Frontal variability.
Journal of Physical Oceanography, 25,
Using a hydrocast survey of the Iceland-Faroe Front (IFF) from October 1992, quasigeostrophic forecasts are studied
to validate their efficacy and to diagnose the physical processes involved in the rapid growth of a cold tongue
intrusion. Explorations of 1) the choice of initial objective analysis parameters, 2) the depth of the unknown level of
no motion, 3) the effects of surrounding mesoscale activity, 4) variations in the boundary conditions, and 5) simple
assimilation of newly acquired data into the forecasts are carried out.
Using a feature validation technique, which incorporates a 1) validating hydrocast survey, 2) satellite SST images, and
3) surface drifter observations, most of the forecasts are found to perform well in capturing the key events of the
validation strategy, particularly the development of the cold tongue intrusion (though it tends to develop somewhat
more weakly and slightly farther downstream than observed). Sharp resolution of frontal structure (to capture seed
anomalies in the IFF, which later can grow to large amplitude) and smooth representation of far-field boundary
conditions (to eliminate spurious persistent inflow/outflow at the boundaries, which can corrupt developing interior
flows) are found to be crucial in generating good forecasts.
An analysis ofthe potential and kinetic energy equations in the region ofthe developing cold tongue intrusion reveals a
clear signature of baroclinic instability. Topography has little influence on this particular instability event because it
tends to be surface intensified and occurs rapidly over a timescale of 3-5 days.