ITCZ

Question 1

What is the ITCZ?

Answer 1

Its an area of low pressure where the Tropical Continental air mass from the Northern Hadley cell, meets the Tropical Maritime air mass from the Southern Hadley Cell

This low pressure causes the rising of the warm air to condense and cause heavy rainfall and thunderstorms

The meeting point of these 2 air masses moves north when the sun moves north of the equator (June) and it moves South of the equator (December) when the sun is overhead, due to the tilt of the earth’s axis

Question 2

Air Masses affecting the ITCZ

Answer 2

The dry, hot and stable Tropical Continental air mass that moves over the Sahara desert, and the dry, wet and unstable Tropical Maritime air mass that moves over the Gulf of Guinea (ocean)

Question 3

South of West Africa description 1 ( initial stage of ITCZ )

Answer 3

Tropical maritime air mass comes from the ocean and meets the Tropical continental air mass at the ITCZ where the sun is directly overhead -
this causes the Tropical Maritime that has absorbed a lot of water, to heat up, rising alongside the Tropical continental forming an area of low pressure and creating large cumulonimbus clouds

Question 4

South of West Africa description 2

Answer 4

Levels of rainfall increase quickly as the ITCZ begins overhead - as the ITCZ moves northwards as the months go by, the rain clouds move with it, causing the amount of rainfall in the South to lessen as the air mass has lost water

The Tropical maritime air mass passes over land as the ITCZ moves Northwards, meaning its source of moisture (the ocean) is further away so there’s less water to be evaporated into the air and transported

Question 5

Middle of West Africa description

Answer 5

Until roughly July time, there’s the dry, desert Tropical continental air mass overhead which lacks moisture

In the middle of the year most of the air masses moisture has already fallen over the South, so the middle regions of WA have a lower peak of rainfall

Question 6

North of West Africa Description

Answer 6

The North of West Africa has the dry, Tropical Continental air mass overhead all year long, so has little to no rainfall, and even when the ITCZ is overhead, there’s little rainfall as the air masses have been overhead for months and so have lost most of their moisture

Question 7

Returning ITCZ to the South of West Africa Description

Answer 7

As ITCZ returns between July and December, the Tropical Continental air mass begins to absorb water again and so rainfall peaks again (to a lesser extent) as the ITCZ moves back down over Africa

Question 8

Summary / explanation

Answer 8

This process explains the drought in ‘winter’ months in the North of Africa, and the second peak of rainfall in the South as the overhead sun heats the air masses again, allowing them to rise, creating precipitation