weather hazards-g3 Flashcards
What is global atmospheric circulation?
Global atmospheric circulation is the transfer of heat from the equator to the poles by the movement of air.
The global atmospheric circulation system is divided into loops(called cells)- each cell has warm rising air that creates a low pressure belt and cool sinking air that creates a high pressure belt. Each hemisphere has three cells.
Why does the air move?
Air moves due to differences in air pressure- winds blow from high pressure areas to low pressure areas.
Explain the global atmoshperic circulation? (its very long and a bit hard, so i don’t expect you to know all of it)
- The sun warms the earth at the equator, causing the air to rise. This creates a low pressure belt.
- As the air rises it cools and moves away from the equator.
- 30* north and south of the equator, the cool air sinks, creating a high pressure belt.
- At the ground surface, the cool air moves either back to the equator(as trade wins) or towards the poles(as westerlies). These winds curve because of the Earth’s rotation-this is called the Coriolis effect.
- 60* north and south of the equator, the warmer surface winds meet the colder air from the poles. The warmer air rises, creating low pressure.
- Some of the air moves back towards the equator, and the rest moves towards the poles.
- At the poles the cool air sinks, creating high pressure. The high pressure is then drawn back towards the equator.
What is the weather like at the equator?
At the equator, the sun is directly overhead- this means the Earth’s surface receives a lot of solar radiation, so it’s hot. Warm, moist air rises and forms clouds, so it rains a lot.
This is the region where tropical rain forests are found
What is weather like at 30* north and south?
Most of the world’s deserts are found at about 30* north and south of the equator. The air is sinking, making a belt of high pressure. The air is not rising so there are only a few clouds forming and very little rainfall. The lack of cloud makes it very hot during the day and very cold during the night as heat is quickly lost from the ground.
What is the weather like at 60* north and south?(explain weather in uk)
The uk is located at about 55* north of the equator. There is rising air and low pressure belts on the ground. Rising air cools, condenses and forms cloud and rain. This is why it is cloudy and rainy in the uk.
What is a tropical storm?
Tropical storms are intense low pressure weather systems with heavy rain and strong winds that spiral around the centre.
What sea temperature do tropical storms form?
Over warm water above 27*C or higher
What is wind shear?
(The difference in wind speed) between higher and lower parts of the atmosphere is low
What time of the year do tropical storms most commonly happen?
They form in the summer an autumn when sea temperatures are at their highest
Where do most tropical storms form?
5 to 15* north ans south of the equator
Why do they not form at the equator?
There is not enough ‘spin’ from the rotation of the earth at the equator. The effect of the Earth’s rotation is called the Coriolis effect.
How do tropical storms form?
The warm surface water evaporates, this evaporated air cools as it rises and condenses to form thunderstorm clouds. This releases huge amounts of energy, producing powerful storms. The rising air creates an area of low pressure, which increases surface winds. Low wind shear prevents clouds breaking up, so the storm stays intact. Several smaller thunderstorms join together to form a giant spinning storm. When surface winds reach an average of 75mph, the storm officially becomes a tropical storm. The storm now develops an eye at it’s centre where air descends rapidly. The outer edge of the eye id the eyewall where the most intense weather conditions(strong winds and heavy rain) are felt. As the storm is carried across the ocean by prevailing winds, it continues to gather strength. On reaching land, the storm’s energy supply(evaporated water) is cut off Friction with the land slows it down and it begins to weaken.
What are the common features of tropical storm?
Tropical storms are circular in shape, symmetrical, hundreds of kilometres wide and usually last 7-14 days. They spin anticlockwise in the northern hemisphere and clockwise in the southern hemisphere.
What is the centre of the storm called and what happens there?
It is called the eye, it is 50km across and this is where cold air sinks towards the ground and warms up. There is very low pressure, light winds, no clouds, no rain and a high temp.
What is the eye wall and what happens there?
The eye is surrounded by the eye wall, where there is spiraling rising air, very strong winds, storm clouds and torrential rain and low pressure.
What happens in the outer parts of the storm?
Towards the edge of the storm, the wind speed falls, the clouds become smaller and more scattered, the rain becomes less intense and the temperature increases.
Does climate change affect tropical storms?
Global average sea surface temperatures have risen by 0.9*C since 1880 and are exchanged to rise more as a result of climate change. Its hard to predict what effect this will have on tropical storms but it may effect their distribution, frequency and intensity.
How does climate change affect the frequency of tropical storms?
Oceans will stay at 27*C or higher for longer each year, so there is a longer period when tropical storms can form. This may mean there are more storms each year.
In the Atlantic, the number of tropical storms each decade seems to have increased.
How does climate change affect the distribution of tropical storms?
As the average ocean temperatures rises, more of the world’s ocean could be above 27*C- this may mean that tropical storms can form in areas that haven’t experienced them before e.g higher altitudes.
