Factors affecting distribution

What is the Inter-Tropical Convergence Zone?

A band of low pressure near the equator where trade winds from the Northern and Southern Hemispheres meet and converge.

What happens when air from the North and South converge?

It forces warm air to rise and form heavy rainfall and frequent thunderstorms.

What is the ITCZ also known as?

‘doldrums’ by sailors due to calm, windless conditions at the surface.

What path does the ITCZ follow?

A path of most intensive solar heating, known as the thermal equator.

What 6 factors affect the distribution of tropical storms?

• Oceans

• High temperatures

• Atmospheric instability

• Rotation of earth

• Uniform wind direction at all levels

How do high temperatures affect distribution?

A sea surface temperature over 26’c is required for tropical storm formation, so are formed in low latitudes during summer, when temp is the highest.

How does atmospheric instability affect distribution?

• Most likely to form in regions of intense atmospheric instability, where warm air is forced to rise.

• ITCZ, where 2 limbs of Hadley Cell converge to form low pressure on the ground.

How does the rotation of the earth affect distribution?

A certain amount of spin is needed.

The Coriolis effect increases with distance away from Equator and explains why storms don’t usually form between 5’ N and 5’ S.

How does uniform wind direction at all levels affect distribution?

• Winds from different directions at altitude prevent a tropical storm attaining height and intensity,

• Vertical development is effectively ‘sheared off’ by multi-directional winds.