Weather Hazards Flashcards
What is global atmospheric circulation
The idea of wind circulating due to different air pressures. Wind always moves from areas of high pressure to areas of low pressure. The winds are part of the global atmospheric circulation CELLS. These cells have warm air rising creating a low pressure belt and cool falling air that creates a high pressure belt.
There are 3 cells in the northern hemisphere and 3 cells in the Southern Hemisphere. Each cell brings different weather.
What weather is found in areas of low pressure
And what is low pressure also known as
Air is rising
Cloudy, rainy, and windy weather. These low pressure systems often begin in the Atlantic, moving eastwards towards the U.K.
They are responsible for the UKs changeable weather.
ALSO KNOWN AS DEPRESSIONS
What weather is found in areas of high pressure
And what is high pressure also known as
The air is sinking therefore no clouds can form so it results in Clear blue skies, sunny and dry
ANTICYCLONE
Describe the movement of wind in global atmospheric circulation
Hot air rises from the equator at 0* then moves 30* north and south of the equator but then sinks as it cools, this is called the Hadley cell.
At 90* north and south of the equator (top and bottom of earth) a wind blows towards the equator however this air heats to quickly and rises and falls at 60* which creates another cell called the polar cell.
In between these cells the Ferrell cell is formed due to the rising polar air at 60* and the cooling air from the Hadley cell at 30*.
What are trade winds
Surface winds blowing towards the equator
In the Southern Hemisphere they blow SE
In the Northern hemisphere they blow NE
What are westerlie winds
Surface Winds blowing towards the poles
These winds blow NW in the Southern Hemisphere and SW in the northern hemisphere
What is the Coriolis effect
Rotation of the earth causes an interesting phenomena on free moving objects on the earth.
Objects in the Northern hemisphere deflect to the right whilst objects in the Southern Hemisphere deflect to the left
How does atmospheric circulation explain the UKs mild, cloudy and wet weather?
Our air is blown from the Atlantic Ocean in westerly winds, these bring depressions (wind and rain).
The UK is found South of the 60N line of latitude, in the mid latitudes. On the boundary of cold Polar air moving south the North Pole and warm sub tropical air moving north from the equator.
How does global atmospheric circulation cause large temperature ranges from day to night in deserts
Majority of worlds deserts are either found 30N and 30S of the equator. Sinking air is found here which creates a belt of high pressure called the sub tropical high. No air rises therefore no clouds form therefore makes the climate very arid. Lack of clouds means day is hot and nights are cold.
What is a tropical storm and what are they called in other countries
A storm that develops in the tropics. In the USA and Caribbean these storms are known as hurricanes, In Southeast Asia and Australia they are called cyclones and in the Philippines they are called typhoons.
These storms can cause devastation to islands and coastal locations.
Distribution of tropical storms / location
Located on and 30n / 30s of the equator
Formation of a tropical storm
1-warm ocean
2-air is drawn to the centre of the storm
3- evaporation occurs
4- warm air rises and cools
5-air condenses to form clouds
6- 15-20km above sea level winds spiral outwards
Why do tropical storms spin
Spin because of the Coriolis effect, which causes warm rising air to bend and spin.
This has been evident through satellite images; also hurricanes in the northern hemisphere bend to right and swirl anti clockwise whereas in the Southern Hemisphere they bend to the left and swirl clockwise.
What happens to a tropical storm when it reaches land
They lose their energy source from the sea which powered them. Moreover as they pass over land, friction slows them down. The loss of energy makes them change direction.
Life span of a tropical storm
One to two weeks
