Chapter 7: APPLICATIONS
Figure 7-17 shows the results of modeling surface renewal in
comparison with the traditional parameterization of interfacial air-sea gas
exchange. The contribution of wave-breaking patches to the interfacial gas
flux represented by formula (7.25) for w s
h = 1 m is shown by dashes.
Differences between the traditional parameterization and the renewal model
are observed under low and high wind speed conditions. In contrast to the
traditional parameterization, the renewal model predicts non-zero interfacial
gas transfer velocities under calm weather conditions (depending on the heat
flux) and smaller transfer velocities at high wind speeds.
For highly soluble gases (like CO 2 ) the interfacial gas exchange may
exceed the bubble-mediated gas exchange even under relatively high wind
speed conditions and is therefore believed to contribute substantially to the
global air-sea gas exchange (Woolf and Thorpe, 1991; Soloviev and
2001).
7.5.3 Bubble-mediated component
Bubbles generated by wave breaking can significantly enhance the airsea gas exchange under high wind speed conditions, especially for low
solubility gases. The asymmetry between evasion and invasion, solubility
dependence on sea surface temperature and salinity, and equilibrium
supersaturation caused by bubble gas transfer make the problem of
parameterization of the bubble-mediated gas transfer quite complicated.
Several studies have been performed in this area (see reviews in Woolf
and Thorpe (1991), Keeling (1993), and Asher and Wanninkhof, 1998). The
study of Merlivat et al. (1993) resulted in the following parameterization for
the bubble mediated gas transfer
1
1
/
m
n
b
c
K W a
b
Sc
D
D
c
(7.26)
where D is the Ostwald solubility coefficient (dimensionless), a 1 and b 1 are
empirical coefficients (which, strictly speaking, may be different for evasion
and invasion), and W c the fractional area coverage of actively breaking
waves defined by (6.14). Note that (7.26) is specific to evasion when the airwater concentration is not near equilibrium (i.e.,
/(
) 1
)
w
a
C S p
P
!! ' .
Woolf (1997) proposed parameterizing the bubble-mediated gas transfer
based on the asymptotes at large and small values of the solubility
coefficient Das follows:
1.2
1/1.2
0.5
/ 1 14
b
c
K bW
Sc
D
D
ª
º
«
»
¬
¼
(7.27)
485
,
Schl ssel
ü
Figure 7-17 shows the results of modeling surface renewal in
comparison with the traditional parameterization of interfacial air-sea gas
exchange. The contribution of wave-breaking patches to the interfacial gas
flux represented by formula (7.25) for w s
h = 1 m is shown by dashes.
Differences between the traditional parameterization and the renewal model
are observed under low and high wind speed conditions. In contrast to the
traditional parameterization, the renewal model predicts non-zero interfacial
gas transfer velocities under calm weather conditions (depending on the heat
flux) and smaller transfer velocities at high wind speeds.
For highly soluble gases (like CO 2 ) the interfacial gas exchange may
exceed the bubble-mediated gas exchange even under relatively high wind
speed conditions and is therefore believed to contribute substantially to the
global air-sea gas exchange (Woolf and Thorpe, 1991; Soloviev and
2001).
7.5.3 Bubble-mediated component
Bubbles generated by wave breaking can significantly enhance the airsea gas exchange under high wind speed conditions, especially for low
solubility gases. The asymmetry between evasion and invasion, solubility
dependence on sea surface temperature and salinity, and equilibrium
supersaturation caused by bubble gas transfer make the problem of
parameterization of the bubble-mediated gas transfer quite complicated.
Several studies have been performed in this area (see reviews in Woolf
and Thorpe (1991), Keeling (1993), and Asher and Wanninkhof, 1998). The
study of Merlivat et al. (1993) resulted in the following parameterization for
the bubble mediated gas transfer
1
1
/
m
n
b
c
K W a
b
Sc
D
D
c
(7.26)
where D is the Ostwald solubility coefficient (dimensionless), a 1 and b 1 are
empirical coefficients (which, strictly speaking, may be different for evasion
and invasion), and W c the fractional area coverage of actively breaking
waves defined by (6.14). Note that (7.26) is specific to evasion when the airwater concentration is not near equilibrium (i.e.,
/(
) 1
)
w
a
C S p
P
!! ' .
Woolf (1997) proposed parameterizing the bubble-mediated gas transfer
based on the asymptotes at large and small values of the solubility
coefficient Das follows:
1.2
1/1.2
0.5
/ 1 14
b
c
K bW
Sc
D
D
ª
º
«
»
¬
¼
(7.27)
485
,
Schl ssel
ü