How are extreme weather events increasingly hazardous for people?
What are tropical cyclones?
large-scale, rotating storms that form over the oceans in tropical areas
have different names depending where in the world they come from
north atlantic ocean and the eastern North Pacific
hurricanes
Philippines, Japan and China
typhoons
Indian and South Pacific
cyclones
Tropical cyclone structure
Above the tropical cyclone
a dense canopy or covering of cirrus cloud
caused by the massive uplift of warm, moist air into the atmosphere
makes it hard to spot the cyclone when its forming
the centre of the cyclone
swirling around it are rain bands
rain banks
high banks of cloud that can stretch out 1000km from the cyclone centre
produce heavy rain and strong winds
the eye
surrounded by eye wall
thick bank of cloud
rises 15km into the atmosphere
has the heaviest rain and strongest winds
Formation of tropical cyclones
form in tropical areas
needs several triggers conditions to fully converge into a tropical cyclone
high temperatures cause air to rise away from the ocean surface
those rising air causes thunderstorms
sometimes these storms group together
creates a strong flow of warm, rapidly rising air
this produces an area of extreme low pressure
ocean temperature has to be above 26.5
source of moist warm air
normally warmer than 26.5
time of year when ocean water is at its warmest
wind converging at the ocean surface
causing air to rise
formation away from the equator
so that the Coriolis effect will cause the storm to rotate
storm rotates
winds accelerate inwards and upwards
makes depression stronger
this forms a cyclone
dry and calm
only place for kilometers where the air is sinking
Tropical cyclones source areas and tracks
Why do tropical cyclones spin
rotation
key charecteristic
gives them their spiral appearance
strong winds
caused by air rushing from an area of high pressure to an area of low pressure
strong winds
affected by Corolis Effect
caused by air rushing from an area of high pressure to low pressure
deflects rushing winds due to the spin of the Earth
makes all Northern Hemisphere tropical cyclones spin counter-clockwise
makes all tropical cyclones in the Southern Hemisphere spin
where a tropical cyclone is formed
source area
has trigger conditions needed for tropical cyclone formation
sea water temperature 26.5 or more
Northern tropics
temperature usually reached between June and November
Southern tropics
temperature usually reach between April and November
has seasonal distribution
tropical cyclones move away from their source area
they follow the direction of the prevailing winds and ocean current
where tropical cyclones travel is called their track
cyclones curve
when winds in the middle and upper atmosphere change direction