Ocean–Atmosphere Interactions - Ocean in the Earth System - page 115

strong horizontal pressure forces. This is the main source of the ocean's
dynamic on a large scale.
Figure 3.2. Terms of the energy balance at the sea's surface,
in zonal average (from [DA 94])
C OMMENTARY ON F IGURE 3.2.- The incident solar energy (marked as
Q SW on this diagram) is at its maximum in the tropics. The surface
temperature being the highest in this latitude belt, the long wave
fluxes (Q LW ), sensible heat (Q S ) and latent heat (Q L ) are also at their
highest there. It can be observed from the net balance (flux entering
the ocean, bottom diagram) that the sum of these terms displays a
marked maximum near the Equator (precipitations in the equatorial
belt greatly exceed evaporation).
3.2.3. Water exchanges between the ocean and atmosphere
We have seen that evaporation contributes to the energy balance at
the surface. However, there is also a transfer of matter involved,
contributing, as with precipitations, to the water balance at the surface:
-in the atmosphere, evaporation from the sea surface is a
component of the hydrological cycle, where more than 80% of
evaporation occurrs over the oceans. Let us remember that water, in its
different states, strongly contributes to the Earth's radiative balance, in
its vapor stage as a powerful greenhouse gas and through the screening