Mean Velocity Vectors |
||
|
The
2°x2° binned mean velocity fields from the drifters are
regarded as "truth" when they are compared with the model fields. To be
comfortable with this approach, unbinned velocity estimates from the drifters
were compared with historical estimates in key regions. The maximum drifter
speed in the GS (226 cms-1) agrees well with the 200 cms-1
measured by Johns et al. (1995). The drifters reach 85 cms-1 in
the NwAtC (119 cms-1 in the 6-hourly observations), roughly in
agreement with the 110 cms-1 noted by Poulain et al. (1996). Peak
speeds observed in the EGC and WGC (123 cms-1 and 142 cms-1,
respectively) are notably higher than the 70 cms-1 reported by
Krauss (1995), due perhaps to a more extensive data set and sampling closer
to the cores of the currents. Mean values for the region south of Iceland and
west of Scotland, most of which are from 0.5 to 5cms1,are on the
same order as the 0.7 cms-1 to 4.7 cms-1 cited by Otto
and Van Aken (1996). |
|
|
|
In the
0.28° field we observe the
unrealistically large anticyclone at 37°N near
Cape Hatteras that was noted by Maltrud et al. (1998) to be responsible for
pushing the GS separation point too far to the north. The eastward
displacement of the Northwest Corner to the mid-basin (30°W, 46° to 48°W) first noted by Fu and Smith (1996) and the
unrealistic coherent zonal flow around 25° to 28°N across the full extent of the basin are also seen. |
|
|
|
In the
0.1° field, these erroneous features are no
longer present and the flow fields in these regions are much more realistic
than the 0.28° field, however
some differences with the observations are seen. The meridional extent of the
GS after it separates near Cape Hatteras is too large and the GS is less
coherently directed toward the northeast. |
|
|
|
|
||
|
|
|
|
