Ch 9.3 What is atmospheric motion? Flashcards
1
Q
What is the definition of air pressure?
A
Air pressure is the force exerted by the atmosphere on the earth’s surface.
2
Q
What are the factors affecting air pressure?
A
- Altitude.
- Air temperature.
- Air movement.
3
Q
How does altitude affect air pressure?
A
- In the lower atmosphere, air pressure decreases with increasing altitude.
- At mountain peaks, the overlying atmosphere is thinner and the air is lighter. Therefore, the air pressure is lower.
- At the foothills, the overlying atmosphere is thicker and the air is heavier. Therefore the air pressure is higher.
4
Q
How does air temperature affect air pressure?
A
- Air pressure decreases with increasing air temperature.
- When the air is heated, it expands and rises. Air near the ground becomes less dense. Air pressure decreases.
- When air is cooled, it contracts and sinks. Air near the ground becomes denser. Air pressure increases.
5
Q
How does air movement affect air pressure?
A
- When air converges near the earth’s surface, it rises. Density of air becomes lower near the earth’s surface. Air pressure decreases.
- When air sinks, it diverges near the earth’s surface. Density of air becomes higher near the earth’s surface. Air pressure increases.
6
Q
What is air pressure belts?
A
There is an uneven distribution of insolation on the earth’s surface. This results in great differences in air temperature between the poles and the Equator. The resulting air movements create the four major air pressure belts.
7
Q
What are the four pressure belts?
A
- Equatorial low (10N to 10S)
- Subtropical highs (Around 30N and 30S)
- Subtropical lows (Around 60N and 60S)
- Polar highs (Around 90N and 90S)
8
Q
What is the air temperature in equatorial low (ITCZ)?
A
High as the regions receive much insolation.
9
Q
What is the air movement in equatorial low?
A
- Air heats up, expands and rises.
- Air converges and rises.
10
Q
What is the air pressure in equatorial low?
A
Low
11
Q
Why is equatorial low is also called the ITCZ?
A
As equatorial low is a region where the trade winds converge, it is also referred to the Intertropical Convergence Zone (ITCZ).
12
Q
What is the air temperature in subtropical highs?
A
Moderate
13
Q
What is the air movement in subtropical highs?
A
- Rising air at the top reaches the top of the lower atmosphere. It cannot rise further and is forced to move towards the poles.
- When the air reaches around 30N and 30S, it sinks and diverges at the earth’s surface, with some air moving towards the Equator, and the other moving towards the poles.
14
Q
What is the air pressure in the subtropical highs?
A
High.
15
Q
What is the air temperature in subpolar lows?
A
Cool.
16
Q
What is the air movement in subpolar lows?
A
Cool air from polar highs moves towards the Equator and converges with warm air from subtropical highs at around 60N and 60S. The lighter warm air rises.
17
Q
What is the air pressure in subtropical lows?
A
Low.
18
Q
What is the air temperature in polar highs?
A
Extremely low due to the small angle of the sun.
19
Q
What is the air movement in polar highs?
A
Cold air contrasts and sinks.
20
Q
What is the air pressure in polar highs?
A
High.
21
Q
What is the relationship between air pressure and winds?
A
- Winds are created by the horizontal movement of the air that is generated from the difference in air pressure on the ground. Winds blow from high-pressure areas to low-pressure areas.
- Pressure gradient controls the wind direction and wind speed. It results in the pressure gradient force, which directs winds to below from high-to-low pressure areas. The steeper the pressure gradient, the stronger the wind.
22
Q
What is the mathematical expression of pressure gradient?
A
Difference in air pressure/ distance.
23
Q
What is coriolis force?
A
The earth rotates on its axis from west to east. In the Northern Hemisphere, wind is deflected to the right of their path of motion. In the Southern Hemisphere, it is deflected to the left. The force that caused the deflection of winds is called the Coriolis force.
24
Q
What is trade winds?
A
- They blow from the subtropical highs to the equatorial lows.
- They are north-easterlies in Northern Hemisphere and south-easterlies in the Southern Hemisphere.
25
What is westerlies?
1. They blow from the subtropical highs to the subpolar lows.
2. They are south-westerlies in the Northern Hemisphere and north-westerlies in the Southern Hemisphere.
26
What is polar easterlies?
1. They blow from the polar highs to the subpolar lows.
2. They are north-easterlies in the Northern Hemisphere and south-easterlies in the Southern Hemisphere.
27
What is the Intertropical Convergence zone?
The contact zone where trade winds from the north and south converge and rise.
28
What is polar front?
The boundary at around 60N and 60S where cold air from the poles/ polar high meets the warm air from the subtropical highs. The two air masses converge and the lighter warm air rises
29
What is the shifting of air pressure belts, wind belts and the ITCZ in July?
1. The air pressure belts, wind belts and ITCA shift northwards.
2. In July, the overhead sun moves to around 23.5N. The hottest belt of the earth shifts northwards. It brings the air pressure belts, wind belts as well as the ITCZ northwards for around 5 to 15 degrees of latitude.
3. The south-east trade winds shift northwards and cross the Equator to the Northern Hemisphere. They are then deflected into South-west trade winds.
30
What is the shifting of air pressure belts, wind belts and the ITCZ in January?
1. The air pressure belts, wind belts and the ITCZ shift southwards.
2. In January, the overhead sun moves to around 23.5S. The hottest belt of the earth shift southwards. It brings the air pressure belts, wind belts and the ITCZ southwards for around 5 to 15 of latitude.
3. The north-east trade winds shift southwards and cross the Equator to the Southern Hemisphere. They are then deflected into north-west trade winds.
31
What is the tri-cellular model of atmospheric circulation?
1. Hadley cell.
2. Ferrel cell.
3. Polar cell.
32
What is the region of the hadley cell?
At the equatorial low.
33
What is the region of the ferrel cell?
At about 30N and 30S.
34
What is the region of the polar cell?
At 90N and 90S.
35
What is the detail of the air movement of the hadley cell?
1. At the equatorial low, the high temperatures cause air to rise. When the rising air reaches the top of the lower atmosphere, it is forced to move towards the poles.
2. The air aloft converges with the air of the Ferrel cell at about 30N and 30S. The air descends.
3. As the air reaches the earth's surface, some of the air moves towards the Equator as trade winds.
4. Trade winds energy at the ITCZ.
36
What is the details of air movement of the ferrel cell?
1. As the descending air reaches the earth's surface at about 30N and 30S, some of the air moves towards the subpolar low as westerlies.
2. These winds meet the cold polar easterlies about 60N and 60S. Warmer and less dense air from the subtropical highs rises above the cold air at the polar front.
3. When the rising air reaches the top of the lower atmosphere, some of the air moves equatorward and descends at the subtropical highs.
37
What is the details of the air movements of the polar cell?
1. At the polar highs, the low temperatures causes air to descend.
2. The cold air moves towards the subpolar lows as polar easterlies.
3. These winds converge with the westerlies from the subtropical highs at about 60N and 60S. The warm air rises at the polar front.
4. When the rising air reaches the top of the lower atmosphere, some of the air moves towards the poles.
38
What is the pattern of air pressure and the ITCZ in July?
1. All pressure belts shift towards the north.
2. The equatorial low/ ITCZ extends to cover the Asian continental interior and North America. Intense low-pressure cells develop over the land.
3. In the Northern Hemisphere, the subtropical high is broken into cells over the sea. In the Southern Hemisphere, it extends over the lad\nd.
4. In the Northern Hemisphere, the subpolar low is broken. In the Southern Hemisphere, it forms a continuous belt over the sea.
39
Why is the pattern of air pressure and the ITCZ in July like that?
1. In northern summer, land heats up more rapidly than the sea.
2. High air temperature over the land.
3. Lower air density over the land.
4. Low air pressure over the land.
40
What does the reasons of pattern of air pressure and the ITCZ lead to?
1. Low pressure belts and the ITCZ shift northwards, intensity and extend over the land.
2. Intense low pressure cells develop over the land.
3. Higher pressure belts are broken and form high-pressure cell over the sea.
41
What is the pattern of air pressure and the ITCZ in January?
1. All pressure belts shift towards the south.
2. The equatorial low/ ITCZ extends over central Africa, Northern America and Central South America.
3. In the northern hemisphere, the subtropical high extends over the land mass of Asia and North America. Intense high-pressure cell develops over the land. In the Southern Hemisphere, the subtropical high is broken and forms high-pressure cells over the sea.
4. In a northern hemisphere, the subpolar low is broken. In the Southern Hemisphere, it forms a continuous belt over the sea.
42
Why is the patterns of air pressure and the ITCZ in January like that?
1. In northern winter, land cools down more rapidly than the sea.
2. Lower air temperature over the land.
3. Higher air density over the land.
4. Higher air temperature over the land.
43
What does the reasons of pattern of air pressure and the ITCZ in January lead to?
1. High pressure belts and ITCZ shift southwards, intensify and extend over the land.
2. Intense high-pressure cells develop over the land.
3. Low pressure belts are broken and from low-pressure cell over the sea.
44
How does the world wind pattern work?
The prevailing wind blows from high-pressure cells to low-pressure cells. The world wind pattern is quite different from the planetary wind system. Seasonal change of the effect of land and sea and the overhead sun disturb the pattern of air pressure belts. This affects the pattern of the world winds.
45
How does the shifting of the ITCZ affect the trade winds in Asia in July?
In July, the ITCZ shifts northwards with the overhead sun. As it extends into the interior of the Asian continent, it brings the trade winds with it. The south-east trade winds from the Southern Hemisphere move northwards the Equator. As they cross the Equator, they are deflected by the Coriolis Force to become south-west trade winds.
