weather hazards + climate change Flashcards
when air sinks what pressure belt does it create
high pressure
when air rises, areas of what pressure are created
low
which direction do winds move in
from areas of high pressure to areas of low pressure
why is it cloudy and wet in the UK
- the UK is close to the boundry of cold polar air movign down from the north and warm sub-tropical air moving up from the south
- the boundry is unstable
- there is rising air and low pressure belts, the rising air cools, condenses and forms cloud and rain
why is it hot and dry in the desert (but cold at night)
- found about 30 degrees north and south of Equator
- here the air is sinking, making a belt of high pressure
- air isn’t rising so few clouds forming and little rainfall
- lack of cloud makes it hot during the day (due to direct sun) and cold during the night as heat is lost quickly from the ground
Why is it hot and humid at the equator and what would you find there
- air is rising and there is another belt of low pressure
- much hotter than UK due to sun directly overhead
- often cloudy with high rainfall due to rising air
- this is where tropical rainforests are found
what is a tropical storm
- a large storm that develops in Tropics
what are tropical storms called in the USA and caribbean
hurricanes
what are tropical storms called in south-east Asia and Australia
cyclones
what are tropical storms called in Japan and the Philippines
typhoons
why do they form in the tropics
because they from over warm oceans (above 27 degrees)
What seasons do they form in and why
Autumn and summer when sea temperatures are highest
Why are tropical storms not found at the equator
because there is not enough ‘spin’ from the rotation of the earth (coriolis effect)
how do tropical storms form
- strong upward movement of air draws water vapour up from warm ocean surface
- evaporated air cools as it rises and condenses to from thunderstorm clouds
- as air condenses it releases heat which powers the storm and draws up more water
- several smaller thunderstorms join to froma a giant spinning storm
- when surface winds reach high enough, the storm officially becomes a tropical storm
- now develops an eye (calm spot) and eye wall (most intense area)
- as storm is carried across ocean by prevaiing winds, it gathers strength
- on reaching land, the storms energy supply (evaported warm water) is cut off. Friction with land slows it down and causes it to weaken
How strong do the surface winds need to be for a storm to be a tropical storm
120 km per hour