Posted by rhines on November 09, 2000 at 19:22:07 (UTC):
In Reply to: ABYSSAL "STORMS" = NEARLY BAROTROPIC - IZZAT CLEAR? posted by Watts on March 31, 2000 at 12:38:20:
: Question for poster visitors after visiting the site:
: Was it made clear ednough to you that the color-coded
: cyclones and anticyclones (which we measured at 3500 dbar)
: are REALLY nearly depth-independent?
: i.e. they exert important
: influence up thru the thermocline to the sea surface
: (thus driving important cross-frontal exchange, which is
: the topic of the Lindstrom papers (see Bibliog).
: There are two good ways to appreciate the barotropic
: (nearly depth-independent) nature
: of these "storms":
: (1) the Savidge and Bane citations study this issue;
: (2) the upper Gulf Stream shear adds to but does not
: erase these deep ('reference') velocities, which therefore
: extend up through the whole water column. Summed together,
: the current turns with height, as is also observed in the
: atmospheric jet stream. Meteorologists call this turning
: "backing" or "veering".
This is a great example of the deep barotropic
'reach' of large-amplitude eddies, one that would be
good to show students. Barotropization is a widespread
phenomenon, but its workings in the presence of a
stat. steady jet have always intriqued me...I recall
that in models the barotropic mode grows downstream,
somewhat as it does in time, in simple initial
value problems with boxes of eddies. For a pretty
view of the barotropic development in an atmospheric
jet see the Orlanski et al. or al. et Orlanski
paper in latest JAS (1xi2000).
Also re waves section, we sat for years
at Site D (39-10N, 70W) watching deep-intensified
topographic waves shooting up from the Stream.
There, there seemed to be a variety of ray
directions including some low freq modes pushing
nearly along depth contours. Nice movie here.