ESS228
Prof. Jin-Yi Yu
What does the Geostrophic Adjustment Tell Us?
•An important feature of the response of a rotating ftuid
to gravity is that it does not
adjust to a state of rest, but rather to a geostrophic equilibrium.
•The Rossby adjustment problem explains why the
atmosphere and ocean are nearly
always close to geostrophic equilibrium, for if any force tries to upset such an equilibrium. the gravitational restoring
force acts quickly to restore a
near-geostrophic equilibrium.
•For deep water in the ocean, where H is 4 or 5 km. c is
about 200 m/s and therefore
the Rossby radius a = c/f ~ 2000 km.
•Near the continental shelves, such as for the North Sea
where H=40m, the Rossby
radius a = c/f ~ 200 km. Since the North Sea has larger dimensions than this, rotation has a strong effect on transient
motions such as tides and surges
in that ocean region.