Properties of Clouds and Cloud Systems
205
with frequent occurrence of cumulus clouds (low-level cumuloform) and/or cirrus (high-level
cirroform) clouds, whereas foul weather clouds producing precipitation are associated with cumulonimbus (vertically extensive cumuloform) clouds and nimbostratus (vertically extensive
and thick stratoform) clouds. Figure 9.10 compares the zonal average amounts of cirrus and
cumulus as determined from both surface and satellite observations. Both these types of clouds
have relatively uniform latitudinal distributions. Cumulonimbus and nimbostratus clouds, together with all high clouds, have noticeable concentrations in the tropics and midlatitudes,
respectively, associated with the regions that have the most frequent and active storms in our
atmosphere. These locations are also associated with higher total cloud amounts (Figure 9.7).
Mean Summer Zonal Cloud Amount
(a) Solid = ISCCP Cirrus+Cirrostratus, Dashed = SOBS Cirrus
..
Land
10
Water
10
Global
...
~ .. -~.
' .
...
"
., ,. ,
, '.
'. '"
...
80
8 •
.. .
••
• •
30
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30
, :
..
,.
..
..
... "
-'
-10
-..
-10
'. "
-30
- 30
-30
' .. ::..
-4'
-..
....
-..
' "
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-so
- 80
-so
' : ::.'.'
: ..
.--...
-,.
-,.
. .
-00
- 00
-00
•
• 0
o •
30
.. 0 .0 20 '0 . . • •• o • 30 ..
(b) Solid = ISCCP Cumulus, Dashed = SOBS Cumulus+Fog
00
Land
10
Water
.. Global
70
70
,. ' .
80
80
:
80
••
••
. .
,.
30
,.
10
"
"
-..
- 10
:
- 30
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:-'
-.. --so
""" 1/0'
-80
-70
-,.
-70
- 00
-DO
-00
0
10
'0
30
.. • •• .. '0 .. 0 10 .. ,. ..
Figure 9 .10: Zonal, seasonal mean (a) cirrus and (b) cumulus cloud amounts from surface
weather observations (SOBS - dashed lines) and from satellite (ISCC? - solid lines) .