3. Weather Hazards Flashcards
How does air always move?
from high to low pressure - causes wind
what is wind
large scale movements of air due to differences in air pressure
Why is there air pressure on earth?
due to the uneveness of of the suns heat on the earth
Does hot air rise or sink?
hot air rises and cool air sinks
where are the rays from the sun most direct to the eart
at the equator
What happens in a Hadley cell
- trade winds blow the air from the tropical regions to the equator
- air is heated due to the concentration of the suns rays at the equator and rises up
- air flows to high latitudes (30-40 degrees)
- here it becomes cooler and sinks over subtropucal regions, causing dry, cloudless air , and air warms as it descends
- this causes warm dry climates, such as deserts
What happens in a Ferrel Cell?
- from 30-60 degrees North and South
- air sinks at the border of the Hadley cells and then goes east due to westerlies winds and rises at the border with polar cells as it gets warmer then goes west due to winds and becomes colder and sinks
- accounts for frequently unsettled weather, such as in the UK
What happens in a polar cell?
- 60-90 degrees North and South
- air is cold here and sinks to form high pressure at the highest latitudes (90)
- cold air goes to border between ferrel cell and is slightly warmed before returning at altitude to the poles
What is the Coriolis effect?
- the appearance that global winds and ocean currents curve as they move
- the curve is due to the earths rotation in its axis, which forces winds to move diagonally
- northeren hemisphere causes wind curves to thr ight, while in the south it is to the left
What are prevailing winds?
- the direction the winds most frequently blow from (for UK it is south westerly)
What are trade winds?
- prevailing winds that blow towards the equator on the left because of the coriolis effect
What are westerlies?
prevailing winds between 30-60 N/S that blow from west to east due to the coriolis effect
What are easterlies?
prevailing winds that blow from the east to the west between 60 - 90 N/S due to the coriolis effect
What are the effects of climate change on tropical storms?
- global temperatures will rise due to climate change and global warming
- this means more of the world’s oceans will be above 27 degrees so more areas of the world will experience tropical storms
- oceans will stay at 27 degrees of higher for more of the year, so the frequency of storms will increase
- high temperatures mean storms will be stronger and more frequent
What is a tropical storm?
- a huge storm that forms in the tropics
- called hurricanes, cyclones and typhoons
What are the conditions for a tropical storm to form?
- the ocean needs to be at least 27oC
- Form in the summer and autumn when ocean temperatures are the highest
- Forms between 5 and 30 degrees North and South of the equator due to the equator not having the Coriolis Effect
- Unstable air (hot air rising rapidly) is needed