Geoscience Reference
In-Depth Information
Figure 3.14
Schematic representa-
tion of the energy spectrum of the
sun's radiation (in arbitrary units) that
penetrates the sea surface to depths
of 0.1, 1, 10 and 100 m. This illustrates
the absorption of infra-red radiation by
water, and also shows the depths to
which visible (light) radiation pene-
trates.
Source
: From Sverdrup (1945).
Figure 3.15
Mean monthly variations
of temperature with depth in the
surface waters of the eastern North
Pacific. The layer of rapid temperature
change is termed the thermocline.
Source
: After Tully and Giovando (1963).
Reproduced by permission of the Royal
Society of Canada.
However, the
actual
temperature change is greater in
dry soils. For example, the following values of diurnal
temperature range have been observed during clear
summer days at Sapporo, Japan:
by the number of thermal units required to raise a unit
mass of it through 1°C (4184 J kg
-1
K
-1
). The specific
heat of water is much greater than for most other
common substances, and water must absorb five times
as much heat energy to raise its temperature by the same
amount as a comparable mass of dry soil. Thus for dry
sand,
c
= 840 J kg
-1
K
-1
.
If unit volumes of water and soil are considered, the
heat capacity, ρ
c
, of the water, where ρ = density (ρ
c
=
4.18
10
6
J m
-3
K
-1
), exceeds that of the sand approx-
imately threefold (ρ
c
= 1.3
1.6 J m
-3
K
-1
) if the sand
is dry and twofold if it is wet. When this water is cooled
the situation is reversed, for then a large quantity of heat
is released. A metre-thick layer of sea water being
cooled by as little as 0.1°C will release enough heat to
Sand
Loam
Peat
Clay
Surface
40°C
33°C
23°C
21°C
5 cm
20
19
14
14
15 cm
7
6
2
4
The different heating qualities of land and water are
also accounted for partly by their different
specific heats
.
The specific heat (
c
) of a substance can be represented
