Geoscience Reference
In-Depth Information
where hot, humid air masses are frequent. At
the southwestern foot of Mount Cameroon,
Debundscha (9m elevation) receives 11,160mm
yr
-1
on average (1960-1980) from the south-
westerly monsoon. In the Hawaiian Islands, the
mean annual total exceeds 7600mm on the
mountains, with one of the world's largest mean
annual totals of 11,990 c\mm at 1569m elevation
on Mount Waialeale (Kauai), but land on the lee
side suffers correspondingly accentuated shelter-
ing effects with less than 500mm over wide
areas. On Hawaii itself, the maximum falls on the
eastern slopes at about 900m, whereas the 4200m
summits of Mauna Loa and Mauna Kea, which
rise above the Trade Wind inversion, receive only
250-500mm. On the Hawaiian island of Oahu, the
maximum precipitation occurs on the western
slopes, just leeward of the 850m summit with
respect to the easterly Trade Winds. Measure-
ments in the Koolau Mountains, Oahu show that
the orographic factor is pronounced during
summer, when precipitation is associated with the
easterlies, but in winter, when precipitation is
from cyclonic disturbances, it is more evenly
distributed (
Table 11.3
).
The Khasi Hills in Assam are an exceptional
instance of the combined effect of relief and
surface configuration. Part of the monsoon
current from the head of the Bay of Bengal (see
Figure 11.23
) is channeled by the topography
towards the high ground and the sharp ascent,
which follows the convergence of the airstream in
500
400
300
Warm
200
Cold
100
0
0°S
5°S
10°S
15°S
Figure 11.55
March rainfall along the south-
western coast of Africa (Gabon and Angola) associ-
ated with warm and cold sea surface conditions.
Source: After Nicholson and Entekhabi from Nicholson (1989).
By permission of the Royal Meteorological Society, redrawn.
10
6
9
8
7
5
drier
Trades
4
6
5
3
4
2
3
Figure 11.56
The structure of the sea breeze in
western Colombia.
Source: After Lopez and Howell (1967). Courtesy of the
American Meteorological Society.
2
1
Katabatic
flow
1
moister
cooler, stable
Pacific air
Western Cordillera
0
0
Table 11.3
Precipitation in the Koolau Mountains, Oahu, Hawaii (mm)
Location
Elevation
Source of rainfall
Trade winds
Cyclonic disturbances
28 May-3 Sep. 1957
2-29 Jan. 1957
5-6 Mar. 1957
Summit
850m
71.3cm
49.9cm
32.9cm
760m west of summit
635m
121.0cm
54.4cm
37.0cm
7,600m west of summit
350m
32.9cm
46.7cm
33.4cm
Source:After Mink (1960).
