= =grad P—f ez X V— , p where the Coriolis parameter is
f = 2Q sin tan0, in terms of the angular velocity of the Earth's rotation, Q, plus the longitudi-
s nal angular velocity of the mean circulation, Vwx*(rs cos 0)-1, with rs being the radius of the Earth.
The boundary conditions at the ocean's surface are w w (z = 0) = 0 ,
where Tis the wind stress (2.42). The boundary condition (2.62) [cf. (2.30)] reflects the intuitive notion that, for a small downward diffusion coefficient, kz, a non-zero wind stress will lead to a steep velocity gradient at the ocean surface. Knowledge of kz is limited, and in oceanic calculations kz is often taken as a constant, the value of which is around 10-4 m2 s-1 (Bryan, 1969).
If the density of water, pw, is also regarded as a constant over time intervals much larger than that used in the averaging procedure, then the equation of continuity (2.45) simply becomes div 5
Since the pressure, Pw in (2.61), is related to temperature and salinity through the equation of state, (2.58), a closed set of equations for the oceanic circulation must encompass transport equations analogous to (2.49) for the average values of temperature and salinity, dA * . dA * "+(^w 'grad)A * +ww —-k z d t d'
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