Aj. Miller et al., QUASI-GEOSTROPHIC FORECASTING AND PHYSICAL PROCESSES OF ICELAND-FAROEFRONTAL VARIABILITY, Journal of physical oceanography, 25(6), 1995, pp. 1273-1295
Using a hydrocast survey of the Iceland-Faroe Front (IFF) from October
1992, quasigeostrophic forecasts are studied to validate their effica
cy 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) variatio
ns in the boundary conditions, and 5) simple assimilation of newly acq
uired data into the forecasts are carried out. Using a feature validat
ion technique, which incorporates a 1) validating hydrocast survey, 2)
satellite SST images, and 3) surface drifter observations, mast of th
e forecasts are found to perform well in capturing the key events of t
he validation strategy, particularly the development of the cold tongu
e intrusion (though it tends to develop somewhat more weakly and sligh
tly farther downstream than observed). Sharp resolution of frontal str
ucture (to capture seed anomalies in the IFF, which later can grow to
large amplitude) and smooth representation of far-field boundary condi
tions (to eliminate spurious persistent inflow/outflow at the boundari
es, which can corrupt developing interior flows) are found to be cruci
al in generating good forecasts. An analysis ofthe potential and kinet
ic energy equations in the region ofthe developing cold tongue intrusi
on reveals a clear signature of baroclinic instability. Topography has
little influence on this particular instability event because it tend
s to be surface intensified and occurs rapidly over a timescale of 3-5
days.