2.4) Atmosphere Flashcards
- What is the STRUCTURE of the Earth’s atmosphere?
The Earth’s atmosphere extends from the Earth’s surface to an altitude above 100km, where it merges with space. It is composed of distinct layers.
1. The troposphere contains the vast majority of atmospheric moisture and 75% of all air, water vapour, and dust.
➞ It is the zone where most weather systems develop.
2. The stratosphere contains the ozone layer, which helps to protect life on Earth by filtering out most of the Sun’s harmful ultraviolet rays.
3. Above the stratosphere and starting around 50km above the Earth’s surface is the mesosphere, which protects the Earth from asteroids that burn up in this area and where temperatures begin to decrease rapidly.
4. At 80km above the Earth’s surface, the thermosphere has very thin air, and temperatures here can reach up to 2000℃.
5. At the outer limits of the atmosphere is the exosphere, where it gradually fades into the vacuum of space and where some gas molecules can escape the Earth’s gravitational pull.
- What is the COMPOSITION of the Earth’s atmosphere?
The atmosphere formed as the Earth cooled billions of years ago. It is a blanket of gases which contains solid particles, including volcanic dust and blown soil, and is attached to the Earth by the force of gravity.
The main gases are:
1. Nitrogen (79%)
2. Oxygen (20%)
3. Argon (1%)
4. Trace amounts of water, carbon dioxide (CO2), and methane (CH4)
- What is the Global Energy Budget?
- The Global Energy Budget refers to the balance between incoming and outgoing solar radiation.
- Insolation caries at different times of the year and for different latittudes.
- Approximately, two-thirds of incoming solar radiation is absorbed by the atmosphere (clouds, water vapour, gases, dust) and the Earth’s surface (land, water, plants).
➞ The remainder is reflected by Earth’s surface, clouds, atmospheric gases, and dust.
- What is the albedo?
The proportion of solar radiation that is reflected by a body or surface is known as the albedo.
➞ This can range from a value of 0 (no reflection) to 1 (100% reflection).
-
The average albedo for Earth is 0.31. The amount of reflected energy changes with surface character.
➞ Snow and ice reflect solar energy back into space and have a high albedo, whereas the albedo for forests, oceans, and deserts are low as more energy is absorbed by ground and water.
- What are causes for the variations in the Albedo effect due to CURVATURE of the earth?
CURVATURE of the Earth:
* The Earth is spherical and and because of this, there are variations in the amounts of insolation received in different places.
* Due to the curve of the Earth, the Sun’s rays are concentrated on a much smaller surface area over the Tropical latitudes, resulting in more energy.
* Also, the larger surface area, which can be found at the Poles, means it has a larger area to heat. This means the insolation at the Arctic Circle is stretched therefore is weaker.
- What are the causes for the variations in the Albedo effect due to THICKNESS of the atmosphere?
THICKNESS of the atmosphere:
* The farther from the Equator, the greater the amount of atmosphere the radiation has to penetrate. Therefore, more is lost through the action of scattering, absorption, and reflection.
- At the Equator, there is less atmosphere for the Sun’s rays to pass through so less energy is lost through absorption etc.
- What are the causes for the variations in the Albedo effect due to the TILT of the Earth (seasonal)?
TILT of the Earth (seasonal):
- As the Earth tilts on its axis, the angle of the sun’s rays changes throughout the year. This has an effect on the amount of insolation received by the different areas and at different times of the year.
- Due to the tilt of the Earth, there is no insolation at the poles for 6 months of the year. However, the tropical areas receive insolation all year round because the Sun is directly overhead in the Equatorial and Tropical regions throughout the year.
- What is the tri-cellular model?
- The tri-cellular model:
➞ explains the redistribution of energy from areas of surplus to areas of deficit. - There is a net gain of solar energy in tropical latitudes and a net loss towards the poles due to the angle at which insolation strikes the Earth’s surface.
- Atmospheric and oceanic circulation redistributes this energy:
➞ so energy is moved from areas of surplus (between 38° North and South)
➞ to areas of deficit (above 38° North and below 38° South). - This process maintains the global energy balance.
- Describe the PROCESS of the tri-cellular model.
- At the equator, intense heating of the land causes warm air to rise, creating a low pressure system.
➞ Air rises and spreads out, with some moving northwards. - At around 30° North, air from the Hadley and Ferrel cells sinks, creating high pressure.
➞ Some air returns to the Equator via surface winds for reheating, completing the Hadley cell. - At the poles, air is cold and sinks towards the Earth’s surface, creating high pressure.
- Surface winds from polar regions reach 60°N and rise upwards, creating another area of low pressure.
- As warmer air meets cold air, the polar front is created at an area of low air pressure.
- The southern end of the Ferrel cell is completed with high altitude air sinking at the Horse latitudes (high pressure).
- Describe the PROCESS of the Coriolis Effect.
- The three cell model takes account of the fact that as the Earth rotates from west to east, the Coriolis effect (due to the Earth’s rotation, objects will deflect to the right in the Northern Hemisphere but in the Southern Hemisphere objects will deflect to the left) acts upon them.
- Consequently, the prevailing winds (winds that blow consistently in a given direction over a particular region on Earth) between different areas of high and low air pressure do not travel from North to South as you would possibly expect, but are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
- The Coriolis effect helps to produce the pattern of surface winds.
- What is a biome?
- Biome:
➞ is a major type of ecological community on planet Earth. A biome consists of distinct plants and animals in one large geographical area. - The distribution of biomes is determined by climate. Latitude, air pressure, and winds are important factors that determine the climate of a place.
- How does LATITUDE determine climate/biomes?
Latitude is one of the most important factors in determining global climate patterns.
- In the lower latitudes, such as the Tropics, temperatures are the highest.
➞ This is because the Sun’s rays travel a shorter distance to the Equator (hitting the Earth at less of an angle) and are therefore more concentrated, resulting in higher temperatures. - In the higher latittudes, such as the Polar regions of the world, temperatures are lowest.
➞ This is due to the Sun’s rays travelling a longer distance and being spread over a wider area of the Earth’s surface. When these rays approach the Earth, they do so at a sloping angle, resulting in lower surface temperatures.
- How does HIGH AND LOW AIR PRESSURE determine climate/biomes?
Differences in temperature lead to variations in air pressure around the world.
-
Low pressure areas are created when air rises.
➞ It is called low pressure because the weight of the air above the Earth’s surface is lower than average.
Lower pressure areas are associated with cloud and precipitation (rainfall) because:
1. As the air rises, it cools and condenses to form clouds,
2. The water droplets in the clouds increase in size,
3. They eventually become too heavy to be held and fall as precipitation.
The air above the Equator is very hot and rises, creating an area of low pressure.
➞ The Equator experiences high amounts of rainfall due to this rising air resulting in a warm and wet equatorial climate (e.g., the Amazon and Congo tropical rainforests).
-
High pressure areas are created when air sinks.
➞ It is called high pressure because the weight of the air is above average when it sinks to the Earth’s surface.
Higher pressure areas are associated with dry, warm, and settled weather conditions.
➞ This is because sinking air does not result in precipitation.
- How do WINDS determine climate/biomes?
- The air travels in the upper atmosphere and sinks at approximately 30° North and 30° South of the Equator.
➞ When the air sinks, it creates an area of high pressure. - These high pressure areas experience very dry and warm conditions resulting in a hot desert climate (e.g., the Sahara and Kalahari deserts).
- Winds blow from areas of high to low pressure, which transfers the air from where it is sinking to where it is rising.
- This continual transfer of wind maintains the pressure belts of high and low pressure, which creates different global climatic zones.
