The ITCZ Flashcards
In July the ITCZ
North over Southern Sahara allowing tropical maritime air mass to feed in north from Gulf of Guinea and dominate the areas weather bringing rain
In January the ITCZ
Migrates south
Tropical continental air mass dominates the region bringing drought conditions.
Only coastal areas are affected by tropical maritime and so receive rain
Describe and account for the variation in rainfall across west Africa
West Africa has marked seasonal variations
High annual rainfall near the coast but decreases northwards away from the coast
Seasonal changes are related to the movement of two air masses and the thermal equator
Tropical maritime air mass from the Atlantic Ocean brings rainfall
Tropical continental air mass originates over the Sahara desert and brings warm, dry weather
ITCZ is where the trade winds converge and brings an area of low pressure which brings rainfall
Seasonal movement of ITCZ
Movement connected to
Arrival of seasonal rains in West Africa
Energy
Surplus leads to warming of air near the equator. Becomes less dense and rises
At the ITCZ warm air rises, condenses, forms tall clouds with associated rainfall
Maximum monthly rainfall associated with ITCZ being overhead
During summer months
ITCZ moves North bringing rain. Places to the south of the ITCZ come under the influence of the Tropical Maritime air mass. Hot and humid conditions for longer periods of the year.
In the Southern part of west Africa
Higher total annual rainfall due to presence of this air mass
Peaks of rainfall
Common nearer West African coast due to movement North of the ITCZ in the summer and the return of the ITCZ en route to the equator in the winter
Northern West Africa
Total annual rainfall lower
Long dry season dominates due to tropical continental air mass bringing hot and dry conditions
Total rainfall is highest
In the south along the coast due to mT air mass which is overhead for most of the year
Brings warm, wet conditions - increasing annual rainfall
At point of convergence
Air is heated due to solar energy
Warm air rises leading to the band of rain known as the ITCZ
The ITCZ and its associated band of rain
Tracks North and South over West Africa due to the earths tilt
Places in the South often have
Twin peaks of rainfall (In June and November) as the ITCZ tracks North in the summer and returns South in the winter
Areas in the North
Receive very little annual rainfall as they are influenced by cT associated with warm and dry conditions
cT air mass influenced by
The movement of air over the Sahara desert where it warms but fails to collect any moisture
