Etudes et évaluation de processus océaniques par des hiérarchies ...

4.5. MEAN CIRCULATION AND STRUCTURES OF TILTED OCEAN DEEP CONVECTION111
810 J O U R N A L O F P H Y S I C A L O C E A N O G R A P H Y VOLUME 38
FIG. 3. Correlation C y (500 m, W) for experiments (left) E04 and (right) E34.
C˜ yy, U, y 0 , t Ux, y 0 , z, tUx x, y 0 y, z z, t dx U P
dzP 2 x, y 0 , z, t dx dz
P
U 2 x x, y 0 y, z z, t dx dzC y y, U C˜ yy, U, y 0 , t y0 ,t, 8
tel-00545911, version 1 - 13 Dec 2010
where . y0 ,t is an averaging over values y 0 separated by
1 km and 30 consecutive time instances separated by 3
h during the last 90 h of the experiment. The results of
this analysis are presented in Figs. 3, 4, and 5. The
predictions of Eq. (7) are nicely confirmed as follows:
(i) The maximum correlation of the w component is
displaced about 500 m and 1 km upward for a y distance
y of the two planes of 500 m and 1 km, respectively,
which demonstrates the high correlation along the axis
of rotation; (ii) the same is approximately true for the u
component, but the correlations are only about half,
due to the decorrelation by the generalized thermal
wind.
The cases with stronger forcing look qualitatively the
same. Quantitative changes are due to the increased
horizontal scales in the cases with stronger forcing [rotation
is less efficient in stopping the horizontal growth
of plume structures; see Wirth and Barnier (2005)].
If we suppose that the convective motion is composed
of descending plumes surrounded by upwardmoving
fluid and an isotropic turbulent component, we
can build an analytical model of the convective process,
based on the balance of rotation (f and F), turbulent
friction (), and reduced gravity (g) acting on a convective
parcel of fluid moving with the velocity (u, , w).
More precisely,
f F
f 0
F 0 u
w 0
0
g .
Solving the linear system leads to
9
FIG. 4. Correlation C y (1 km, W) for experiments (left) E04 and (right) E34.