Geoscience Reference
In-Depth Information
(mm)
(
8
C)
(m
2
s
−2
)
(m
2
s
−2
)
(m
2
s
−2
)
(m)
(m)
(m)
Fig. 7.8 Range of parameters
β
0
τ
and
L
, for which turbulence energy pumping during a time
τ
(the values are indicated in the figure) results in (1) an increase (+), a decrease (-) of the maximum
temperature gradient by a quantity, exceeding 10% of the initial value; (2) a change of the sur-
face temperature; (3) a change of the centre-of-mass position. The figures at the isolines indicate
the change in the surface temperature in degrees Celsius and in the centre-of-mass position in
millimeters. Calculations are carried out for
h
1
= 10 m and
H
= 100 m
motion scales, but not towards smaller energies. Such an effect is readily explained.
The point is that the lifetime of a vortex increases with its scale
L
. Therefore, in
the case of a large-scale turbulence a source action of duration
within the range
from 1 to 100 s can be considered instantaneous; only the total amount of energy
β
0
τ
τ
is essential. But a small-scale turbulence, generated by a source of short action,
dissipates before it has time to contribute noticeable changes in the temperature
profile.
The influence of the thermocline depth on the change in the centre-of-mass posi-
tion is insignificant: differences are observed only in the case of large energies
β
0
τ
and scales
L
, i.e. when the water column is mixed until it is practically in a uniform
state. The characteristic value of quantity
z
amounts to several millimeters, which,
however, represents a significant value. By calculations in accordance with formula
δ
