Chemistry Reference
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Fig. 2.
Naturally occurring heat fluxes at the ocean surface and transport mecha-
nisms of heat in the thermal sublayer
In a first realization, Jähne et al. (1989) forced a periodical heat flux
density onto the water surface using a chopped heat source above the water
surface. The temperature response at the water surface was detected with
point measuring radiometer. In a further implementation of this technique,
Haußecker (1996) developed the so-called passive controlled flux method
that estimates the skin-bulk temperature difference under natural heat flux
conditions assuming a surface renewal model. The naturally occurring heat
fluxes at the ocean surface (latent, sensible and long wave radiative heat
flux) cause the surface temperature to decrease or increase depending on
the direction of these fluxes. The net heat flux forces a skin-bulk tempera-
ture difference '
T
across the thermal sublayer, commonly referred to as
the “cool skin” of the ocean (compare Fig. 2).
The high temperature resolution of state-of-the-art infrared imagers al-
lows measurements of the temperature fluctuations at the ocean surface
even under low natural net heat flux conditions (Schimpf et al. 1999). The
net heat flux density
j
h
, skin-bulk temperature difference '
T
and the char-
acteristic time constant
t
* of the transfer process are related by the transfer
velocity for heat,
k
h
, according to (Jähne et al. 1989):
j
D
k
U
h
h
(1.1)
,
h
c
'
T
t
p
*
where
D
h
denotes the molecular diffusion coefficient for heat in water.
Given the net heat flux density, the local heat transfer velocity is deter-
mined by measuring the skin-bulk temperature difference across the ther-
