Theory question 111
West Africa and ECOWAS(a) On an outline map of West Africa, mark and name the (i) approximate position of the ITCZ in January; (ii) low pressure belt in January; (iii) high pressure belt in January; (iv) position and direction of the Tropical Continental Air Mass in January; (v) Guinea current; (vi) Canary current
(b) Discuss the relationship between the pressure belts and rainfall distribution in West Africa.
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(a) ITCZ along about 5-7°N near the coast; low pressure over the Gulf of Guinea/south; high pressure over the Sahara; tropical continental air mass (NE trades/harmattan) blowing from NE to SW over most of West Africa; Guinea current flowing eastward along the coast; Canary current flowing southward off the NW coast
(b) Rainfall follows the movement of pressure belts and the ITCZ: when the sun moves north (March-September) the low pressure and ITCZ shift north and moist tropical maritime air from the south-west brings rain; the south, under maritime air longest, gets the most rain and two peaks; the north gets rain only for a few months; when the belts move south (November-February) the Saharan high pressure sends dry harmattan winds over the region, giving the dry season
Explain rainfall by the yearly shift of the ITCZ.