THE NEAR-SURFACE LAYER OF THE OCEAN
because of temperature and salinity changes, increase of the surface
roughness, damping of short gravity waves, excitation of capillary waves at
higher wave frequencies, and the surface mixing by droplets.
During rainfall the raindrops penetrate to tens of centimeters directly
affecting the near-surface salinity. Rain falling on the sea surface also
establishes a haline diffusive molecular sublayer with a salinity gradient.
et al. (1997) refer to this layer as the freshwater skin of the ocean.
The freshwater skin is only about 50 Pm thick. The salinity difference
developing in the haline diffusive molecular sublayer can to some extent
affect the interpretation of the radar and radiometric observations of the sea
surface at low microwave frequencies. The dielectric constant of water
depends on the sea surface salinity at centimeter wavelengths (Lagerloef et
al., 1995). The dielectric constant change may cause interpretation problems
when remotely measuring wind speed or sea surface temperatures at these
frequencies. The dielectric constant dependence on salinity may also be used
for remote sensing of the sea surface salinity. Though the depth of the haline
molecular sublayer is much less then the penetration depth of the
electromagnetic radiation at these wavelengths, the exponential decay of the
radiation energy entering the ocean can, however, make it sensitive to
salinity changes in the skin layer.
An important effect is the dependence of gas solubility on salinity. For
instance, a 1% decrease of the seawater salinity results in a 0.5% increase of
the CO 2 solubility and 0.1% increase of the O 2 solubility (Stephen and
Stephen, 1964; Riley and Skirrow, 1965).
In view of the different effects that can be expected from rainfall on the
surface molecular sublayer,
et al. (1997) provide a comprehensive
description of the modifications of this layer of the ocean due to
precipitation. According to these authors, the impact of precipitation on the
thermal and diffusive molecular sublayers of the ocean includes the
following processes:
1) The freshwater flux due to rain produces a buoyancy flux in the
near-surface layer of the ocean, which tends to suppress convection
(Ostapoff et al., 1973).
2) Raindrops temperatures are usually lower than the sea surface
temperature (Katsaros, 1976). The precipitation falling into the
ocean results in an interfacial sensible heat flux rs
Q caused by small
drops that do not penetrate into the ocean and in a volume heat flux
rV
Q due to drops submerging into the ocean and gradually mixing
with depth.
3) Changes in the temperature and salinity due to rain mentioned in the
previous two points modify physical constants of sea surface water
(Katsaros and Buettner, 1969). In particular, the kinematic viscosity
120
Schl ssel
ü
Schl ssel
ü
because of temperature and salinity changes, increase of the surface
roughness, damping of short gravity waves, excitation of capillary waves at
higher wave frequencies, and the surface mixing by droplets.
During rainfall the raindrops penetrate to tens of centimeters directly
affecting the near-surface salinity. Rain falling on the sea surface also
establishes a haline diffusive molecular sublayer with a salinity gradient.
et al. (1997) refer to this layer as the freshwater skin of the ocean.
The freshwater skin is only about 50 Pm thick. The salinity difference
developing in the haline diffusive molecular sublayer can to some extent
affect the interpretation of the radar and radiometric observations of the sea
surface at low microwave frequencies. The dielectric constant of water
depends on the sea surface salinity at centimeter wavelengths (Lagerloef et
al., 1995). The dielectric constant change may cause interpretation problems
when remotely measuring wind speed or sea surface temperatures at these
frequencies. The dielectric constant dependence on salinity may also be used
for remote sensing of the sea surface salinity. Though the depth of the haline
molecular sublayer is much less then the penetration depth of the
electromagnetic radiation at these wavelengths, the exponential decay of the
radiation energy entering the ocean can, however, make it sensitive to
salinity changes in the skin layer.
An important effect is the dependence of gas solubility on salinity. For
instance, a 1% decrease of the seawater salinity results in a 0.5% increase of
the CO 2 solubility and 0.1% increase of the O 2 solubility (Stephen and
Stephen, 1964; Riley and Skirrow, 1965).
In view of the different effects that can be expected from rainfall on the
surface molecular sublayer,
et al. (1997) provide a comprehensive
description of the modifications of this layer of the ocean due to
precipitation. According to these authors, the impact of precipitation on the
thermal and diffusive molecular sublayers of the ocean includes the
following processes:
1) The freshwater flux due to rain produces a buoyancy flux in the
near-surface layer of the ocean, which tends to suppress convection
(Ostapoff et al., 1973).
2) Raindrops temperatures are usually lower than the sea surface
temperature (Katsaros, 1976). The precipitation falling into the
ocean results in an interfacial sensible heat flux rs
Q caused by small
drops that do not penetrate into the ocean and in a volume heat flux
rV
Q due to drops submerging into the ocean and gradually mixing
with depth.
3) Changes in the temperature and salinity due to rain mentioned in the
previous two points modify physical constants of sea surface water
(Katsaros and Buettner, 1969). In particular, the kinematic viscosity
120
Schl ssel
ü
Schl ssel
ü