Summary
Summary Tropical cyclones and Subtropical anticyclones - Grade 12 Geography
- Course
- Geography
- Institution
- 12th Grade
A detailed summary of the Tropical Cyclone Chapter for Grade 12 Geography.
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Tropical CyclonesA low pressure cell that develops over warm oceans between
the tropics
General characteristics of a tropical cyclone
● Tropical cyclones develop at the ITCZ, but outside 5º north and south,
because a Coriolis Force is absent on the equator.
● It is an intense low pressure storm which causes a lot of wind and flood
damage.
● Tropical cyclones only form under very specific conditions.
● They are named alphabetically in the season they occur.
Areas where tropical cyclones occur
● Between 30° north and 30° South latitude
● Depend on coriolis Force for formation ( coriolis force is zero at equator)
● different names in different parts of world
○ hurricane - gulf of mexico
○ Typhoons - japan
○ Cyclones - southern africa
○ Willy-willies - australia
● Occur on the east side of continents ( sea is warmer)
● move from near equator towards coast of country
● Reach land then turn East away from coast
Formation of tropical cyclones
● Hot moist air
○ ITCZ - inter tropical convergence zone (area in tropics where 2 sets of
tropical easterlies meet)
○ develop over the sea where the temperature of the water is over 28
degrees
○ a lot of evaporation and very hot, humid, unstable air
○ Occur at Hottest time of year, late summer and early autumn
○ The sea had time to warm during summer
○ in Southern Hemisphere - February to April
● Intense low pressure cell
○ hot air starts rising and forms low pressure cell on surface
○ tropical jetstream in Upper air causes a low pressure cell ( intensifies
low pressure cell on surface)
○ air sucked into low pressure
, ● Coriolis Force
○ Region near equator there is no coriolis Force
○ low pressure cell develops outside the coriolis force will cause went to
Spiral into low pressure cell
○ this intensifies low pressure to create a calm tunnel ( eye of cyclone)
○ wind blows into low in clockwise Direction (southern hemisphere)
○ wind blows into low in anti-clockwise Direction (northern hemisphere)
○ pressure gradient is steep, resulting in winds of up to 300 km/h
how tropical cyclone get energy
● Large scale condensation releases latent heat into atmosphere ( hidden Heat
energy that is given out when water vapour condenses )
● This makes the air unstable and contributes to air rising
● air pressure is so low in the eye that air is sucked down forming calm
cloudless conditions
● air is warmer in the eye due to adiabatic heating (Temperature change due to
change of height and pressure)
Stages of development
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