PhD Thesis Emmanuel Obeng Bekoe - Cranfield University

Emmanuel Obeng Bekoe Phd Thesis Chapter 2 Hydrol, Humid Tropics & Study Area
20
absence of a cold season. The mean annual temperature range i.e. the
difference between the mean of the coolest and the hottest months of the year
is typically between 2 o C and 4 o C. Annual precipitation totals are substantial,
being in excess of 1000 mm, although such regions have wet and dry seasons
(Keller, 1983, Manton & Bonell. 1993). The humid tropics can be further
separated (see Figure 2.3) into one which is affected by tropical cyclones and
one that is not (WMO, 1983). The Non-
Cyclonic Zone
Tropics
Continuously
Humid
Non Cylonic Zone
Seasonally
Humid and Dry
West Africa
Figure 2.3 Illustration of the Tropics (adapted from Trewartha In: WMO
(1983), McGregor and Nieuwolt (1998) & Keller (1983)
Tropical-cyclone sub-region may again be subdivided into two sub-climate
zones: one that is continuously humid and one that is seasonally humid and dry
in terms of rainfall (Keller, 1983; Manton and Bonell, 1993). The continuously
humid zone is mainly found within a relatively narrow band at 3 o N-5 o S latitude.
Most of West Africa (Figure 2.1) lies in the latter i.e. seasonally humid and dry in
terms of rainfall. The emphasis of this research is on West Africa and therefore
further discussion of the humid tropics will be limited to the seasonally humid
and dry region.