Geoscience Reference
In-Depth Information
5.7)
. Additionally, surface snow and ice become relevant at high latitudes. There
is a minimum close to the equator due to the deep cloud cover associated with
the ITCZ, and higher values in the subtropics where the sky is relatively clear.
The two longwave radiation components of the surface heat balance are
drawn in
Figure 5.11
. Terrestrial emission (
Fig. 5.11a)
is proportional to the
fourth power of the surface temperature (Eq. 4.2), so its distribution is similar
to the low-level and surface temperature distributions shown in
Figures 2.6
and
2.15.
The longwave back radiation (
Fig. 5.11b
) is larger at low latitudes
because of the distribution of atmospheric water vapor (
Fig. 2.31)
, which is
a powerful greenhouse gas that occurs in higher concentrations in warmer
regions (see
Figs. 2.30
-2.32
).
(a)
90°N
240
300
240
300
60°N
300
300
360
360
360
360
4
20
360
30°N
420
420
420
Equator
360
420
30°S
420
420
420
360
360
60°S
300
300
300
240
240
180
240
180
90°S
180
0°
30°E
60°E
90°E 120°E 150°E 180° 150°W 120°W 90°W 60°W 30°W 0°
(b)
90°N
240
240
240
180
60°N
240
300
300
300
360
360
30°N
24
0
300
360
360
420
420
Equator
420
420
300
360
360
30°S
360
360
300
180
300
60°S
240
240
120
240
120
180
90°S
120
0°
30°E
60°E
90°E 120°E 150°E 180° 150°W 120°W 90°W 60°W 30°W 0°
Figure 5.11 (a) Longwave radiative emission from the surface. (b) Longwave back
radiation from the atmosphere to the surface. Contour intervals are 30 W/m
2
.
