Geoscience Reference
In-Depth Information
(a)
A-A
´
Warm air
Cool air
Cool air
(b)
B-B
´
Warm air
Cool air
Cool air
(c)
Warm air
Figure 10.9
Vertical
cross-section along (a) the
lines A-A
C-C
´
′
in Figure 10.8c; (b)
the lines B-B
Cool air
Cool air
′
in Figure 10.8c;
and (c) the line C-C
′
in
Figure 10.8d.
Figure 10.9 illustrates typical cloud and precipitation behavior in the vertical
cross-sections along the lines A-A
′
and B-B
′
in Fig. 10.8c, and along C-C
′
in
Fig. 10.8d. The cross-section along line B-B
shows the expected behavior for the
two separated fronts moving to the right, while the line A-A
′
shows the behavior
in a region where the warm air has risen and is still rising above the cold air. The
behavior shown in the cross-section C-C
′
illustrates the behavior when the two
fronts have become occluded and cyclonic activity is at its peak.
′
Cloud genera
Classification of clouds is not straightforward. Cloud morphology and cloud
height are the usual basis for defining cloud genera. The form of cloud is indicated
by the names
cumulus
meaning 'heaped,
stratus
meaning 'layered, and
cirrus
meaning 'fibrous. However, the designation
nimbus
, which indicates rain clouds,
is additionally used as a qualifier.
Cumulonimbus
, for example, describes a cloud
with a heaped form that produces precipitation, a designation that is almost syn-
onymous with a thunderstorm. Cumulus clouds may extend through the tropo-
sphere, and stratus, cirrus, and cumulus may have a height related prefix, such as
alto
, which implies medium height. The main cloud genera currently used are
given in Table 10.3, along with some important cloud characteristics associated
