Climate Hazards Revision

Effects

They are compound hazards:

Heavy rainfall - deposits massive volumes of rain in short time periods.

Strong winds - sustained wind speeds of over 118kmh.

High waves – causing deadly storm surges in coastal areas.

Highly destructive.

Impacts

Physical:

Flooding, mudslides, deforestation, denudation, pollution, death of flora and fauna, coastal saline intrusion.

Human:

Loss of life.

Injury, disease.

Economic loss.

Loss of infrastructure, jobs, services, income, housing, industry, food, crops, cattle, clean water, sanitation, medical resources, boats.

• Tropical storms are one of the most destructive natural hazards in terms of frequency and deaths.

• They are a major threat to densely populated low lying delta areas e.g. Bangladesh; island groupings in the Philippines and Caribbean; and densely populated coastlines such as the Atlantic coast of the USA and Gulf of Mexico.

Formation

• Firstly, tropical storms begin as small scale tropical-disturbances or ‘depressions’ over the sea.
• The sea and air temperature is heated by the sun’s rays to over 27°C.
• Due to the heat, the warmed air rises causing the air pressure to become low and unstable (a disturbance).
• As the warm air rises it holds a large amount of water vapour which cools with height to form clusters of large thunderstorms.
• Fifthly, the rising air spirals upwards creating 119 – 250 Kmh winds moving in an anti-clockwise direction in the northern hemisphere. Clockwise in the southern hemisphere.
• In the middle of these strong winds is a calm area called ‘the eye of the storm’.
• Here cold air sinks to replace the rising warm air and this cycle continues until there is no more latent heat from the ocean or the tropical storm reaches land.
• Lastly, tropical storms can be up to 800km in diameter.

Locations and names

Climate Hazards Revision

• Tropical storms develop between 5 and 20° north and south of the equator, within ‘the tropics’.
• They occur between May to March at different locations around the world.
• Those born in the Atlantic Ocean are called Hurricanes, Western Pacific are Typhoons or Willy-willies, Indian Ocean born are called Cyclones.
• They affect the Gulf of Mexico, the Caribbean, Florida, Madagascar, India, Bangladesh, Vietnam, Thailand, China, Japan, the Philippines,

Indonesia and Australia.

Tropical Storms

• Once wind speeds reach a sustained 37kmh (23mph) they are classed as tropical depressions, at 63kmh (41mph) they are called tropical storms, at 119kmh (74 mph) they are hurricanes.
• Hurricanes bring high-intensity, high-volume rainfall. (Up to 500mm in 24 hours x 200 mile diameter) = flooding.
• 15 metre high waves (above high water mark) are generated in the deep ocean, and up to 6m (above high water mark) on the shoreline = storm surge.

Processes and Case Studies