THE NEAR-SURFACE LAYER OF THE OCEAN
have proposed to separate the spectral band 0.2 to 0.6 Pm into two
subranges, which provides a better approximation of the solar radiation
absorption for the different types of oceanic water. This improvement,
however, has only marginal effect for the upper meters of the ocean.
Formulation (1.61)-(1.62) provides a convenient description for the
volume source
/
R
I
z
w w in equation (1.10). Dependence of the incident solar
radiation in the infrared range on the water vapor content (Ivanoff, 1977)
may, however, affect values of the weight coefficients a 3 - a 9 in Table 1-2.
1.5 Rain Forcing
1.5.1 Dynamics of rain drops at the air-sea interface
Raindrops falling on to the sea surface behave differently depending on
their size and impact velocity and they represent both a surface and a volume
source of freshwater (Schl ssel et al., 1997). Drops of rain typically reach
the sea surface at their terminal velocities, the vertical velocity when the
gravitational force equals the drag force. Small droplets with a low impact
velocity cannot break the surface and thereby accumulate freshwater on top
of the sea surface. Heavier drops with higher vertical velocities can coalesce
into the sea surface with little or no splashing and generate a vortex ring that
penetrates downward into the ocean (Katsaros and Buettner, 1969;
Rodrigues and Mesler, 1988; Hsiao et al., 1988). Alternatively, they repel or
splash with the formation of a Rayleigh jet (which is the jet-like column of
fluid at the sea surface). The occurrence of the Rayleigh jet depends on the
Weber number
1/ 2
/
i
r
s
We w
D
U
V
,
(1.63)
where D is the drop diameter, i
w is the impact (terminal) velocity, r
U the
density of the drop, and s
V the surface tension.
For small Weber numbers the drop entering the ocean directly penetrates
downward without any prominent splash or jet production. For larger Weber
numbers a jet is produced and the vortex formation is deferred until a
secondary drop breaking off the tip of the jet column makes its way into the
ocean. There is a critical Weber number
cr
We at which the transition from the
direct coalescence to the production of a jet and/or splash takes place;
according to Hsiao et al. (1988),
8
cr
We | . Rodriguez and Mesler (1988)
found that the submergence of large primary drops into the water is rather
low due to their high impact velocities, in contrast to secondary ones that
34
ü
have proposed to separate the spectral band 0.2 to 0.6 Pm into two
subranges, which provides a better approximation of the solar radiation
absorption for the different types of oceanic water. This improvement,
however, has only marginal effect for the upper meters of the ocean.
Formulation (1.61)-(1.62) provides a convenient description for the
volume source
/
R
I
z
w w in equation (1.10). Dependence of the incident solar
radiation in the infrared range on the water vapor content (Ivanoff, 1977)
may, however, affect values of the weight coefficients a 3 - a 9 in Table 1-2.
1.5 Rain Forcing
1.5.1 Dynamics of rain drops at the air-sea interface
Raindrops falling on to the sea surface behave differently depending on
their size and impact velocity and they represent both a surface and a volume
source of freshwater (Schl ssel et al., 1997). Drops of rain typically reach
the sea surface at their terminal velocities, the vertical velocity when the
gravitational force equals the drag force. Small droplets with a low impact
velocity cannot break the surface and thereby accumulate freshwater on top
of the sea surface. Heavier drops with higher vertical velocities can coalesce
into the sea surface with little or no splashing and generate a vortex ring that
penetrates downward into the ocean (Katsaros and Buettner, 1969;
Rodrigues and Mesler, 1988; Hsiao et al., 1988). Alternatively, they repel or
splash with the formation of a Rayleigh jet (which is the jet-like column of
fluid at the sea surface). The occurrence of the Rayleigh jet depends on the
Weber number
1/ 2
/
i
r
s
We w
D
U
V
,
(1.63)
where D is the drop diameter, i
w is the impact (terminal) velocity, r
U the
density of the drop, and s
V the surface tension.
For small Weber numbers the drop entering the ocean directly penetrates
downward without any prominent splash or jet production. For larger Weber
numbers a jet is produced and the vortex formation is deferred until a
secondary drop breaking off the tip of the jet column makes its way into the
ocean. There is a critical Weber number
cr
We at which the transition from the
direct coalescence to the production of a jet and/or splash takes place;
according to Hsiao et al. (1988),
8
cr
We | . Rodriguez and Mesler (1988)
found that the submergence of large primary drops into the water is rather
low due to their high impact velocities, in contrast to secondary ones that
34
ü