geography ✿ global hazards (weather)

extreme weather

weather that is unusual and can cause a threat to life

where is the Hadley cell located?

on the equator, between 30°-40° north to south

where is the ferrel cell located?

30°-60° latitude

where is the polar cell located?

60°-90°

how are low pressure belts formed?

what do they result in?

• warm air rises, creating lower surface pressure

• rising air cools and condenses, creating clouds and precipitation

• result in → wet, unstable weather, more precipitation and strong winds

how are high pressure belts formed?

what do they result in?

• cool air sinks, creating higher surface pressure

• air then warms up and dries out

• result in → dry, stable and little precipitation (desert and semi-arid zones)

What type of winds are usually associated with low pressure systems? [2]

high/ strong winds

Explain how the global circulation system causes extremes of rainfall in one part of the world. [2]

• in high pressure areas

• sinking air warms up, so less condensation occurs so no clouds are formed

Explain how the global circulation system causes extremely high temperatures in one part of the world. [2]

• in high pressure areas

• due to sinking air warming up, there are only a few clouds this means there is little clouds to block the sun

Identify the type of natural weather hazard shown in Fig. 1.

drought

explain one way in which global atmospheric circulation creates a climatic zone in the tropics

• there is sinking air at the Tropics

• which means there is no condensation

• so clouds can’t form, leading to dry conditions

explain one way in which global atmospheric circulation creates a climatic zone at the poles

• high pressure is formed at the poles as cold dry air sinks

• which produces stable conditions and little rain

explain one way in which global atmospheric circulation creates a climatic zone at the equator

• the equator is in between the two Hadley cells

• low pressure is created due to rising air warming and condensing, leading to cloud formation

Give two types of extreme weather associated with tropical storms

• heavy rain

• strong winds

describe how a tropical storm is formed

• tropical storms form over warm oceans over 27°c, which provides the energy

• water evaporates, making the air warm and rise, creating low surface pressure

• warm air condenses, creating strong clouds

• the earths spinning makes the storm start to spin

• a calm centre, the eye, is formed with the strong winds in the eye wall

El Niño

when trade winds are weakened/ reversed causes warm water near South America, leading to droughts in Australia

La Niña

when trade winds become stronger, causing warm water near Australia, causing droughts in South America

what are 3 effects of the droughts caused by La Niña and El Niño

• crop failures

• water shortages

• increased risk of wildfires