THE NEAR-SURFACE LAYER OF THE OCEAN
Both a
U and F
' are referenced to the specified height, z, of the mean
quantities above the mean ocean surface (usually z = 10 m).
The bulk-flux formulation for the magnitude of wind stress
1/ 2
2
2
0
0
0
x
y
W
W
W
following from (1.25) and (1.31) is as follows
2
0
1 0
D a
C U
W
U
,
(1.34)
where D
C is the drag coefficient, a
U is the density of air, 10
U is the wind
speed at 10 m height (z = 10 m). Sensible, Q T, and latent, Q E, heat flux are
estimated from the following bulk formulations:
10
0
T
p a a T
a
Q c
C U T T
U
(1.35)
10
0
E
a E
a
Q L C U q q
U
(1.36)
where pa
c is the specific heat capacity of air at constant pressure, C T is the
bulk transfer coefficient for sensible heat, C E is the bulk transfer coefficient
for latent heat, T 0 is the sea surface temperature (SST), T a is the air
temperature at 10 m, q 0 is the saturation specific humidity of air at sea
surface temperature, and q a is the specific humidity of air at 10 m.
For order of magnitude estimates,
3
~ 1.1 10
D
C
u
for U 10 = 5 m s
-1 , while
for wind speeds within the range, 6 m s
-1 < 10
U < 22 m s
-1 , Smith (1988)
suggested a linear relationship
3
10
1 10
0.61 0.063
D
C
U
| u
˜
(1.37)
Smith (1988) also proposed empirical formulae for the sensible and latent
heat transfer coefficients:
3
3
0.83 10 for stable conditions
1.10 10 for unstable conditions
T
C
­
u
®
u
¯
(1.38)
and
3
1.5 10
E
C
u
,
(1.39)
14