Atmosphere Flashcards
Explain why the Earth’s surface only absorbs 50% of the solar energy received at the edge of the atmosphere (8)
- The Earth receives energy from the Sun as short wave radiation, also known as Insolation
- As the radiation passes through the atmosphere, 18% is lost due to absorption
- 15% is absorbed by gases and dust, and 3% is absorbed by the clouds
- A further 26% is lost due to reflection
- 21% is reflected by the clouds and 5 % is reflected by the gases and dust
- This 26% of reflection is known as the Earth’s albedo, and varies throughout the world
- 56% reaches the Earth’s surface
- 6% reflects of the Earth’s surface, so only 50% of the Insolation is absorbed
Explain why there is a surplus of energy at the equator and a deficit of solar energy at the poles (10) [DIAGRAM]
Latitude
• Within the topics, the Sun’s radiation strikes the Earth’s surface at a high angle
- The radiation takes the shortest route to the surface here, so there is less heat lost
- The radiation heats only a small surface, so there is less heat lost
• Within the polar regions, the Sun’s radiation strikes the Earth’s surface at a low angle
- The radiation takes the longest route to the surface here, so there is a lot of heat lost
- The radiation heats a larger surface, so there is more heat lost
Seasons
• The Earth is tilted on an axis, so radiation strikes the surface at different angles during the year
- While the tropics are closest to the sun, the polar regions will be the furthest away from the sun, resulting in a heat deficit
• The Earth is tilted, so hours of daylight vary though out the year
- While the tropics always receive 12 hours of daylight, the polar regions spend half a year with constant darkness, and half a year with daylight
Explain how the currents in the Atlantic Ocean operate to maintain the global energy balance (10)
In the North Atlantic
- Warm water in the Gulf of Mexico expands and moves polewards as the Gulf Stream
- As it moves North, it is deflected by the Coriolis Effect to move North-Easterly
- Prevailing South-Westerlies drag the water even further North-East
- On reaching Europe, some of the current deflects southwards to become the cold Canary current
- Some of this current is deflected northwards as the North Atlantic Drift
- Once past Norway, the North Atlantic Drift meets the North-Easterly winds and returns southwards as the East Greenland Current and the Labrador Current to rejoin the Gulf stream.
- Meanwhile, the Canary current is dragged by North-Easterly trades to the Equator, however can’t go further because it meets South-Easterly trades which moves it along the equator until it joins the Gulf Stream
In the South Atlantic
- Water moves the opposite way in the South Atlantic
- Instead of a figure-of-eight pattern, the water makes a single gyre
- Water moves southwards from the Tropics as the Brazilian Current, but is deflected left by the Coriolis effect towards the African coast, where it is deflected Northwards as the Benguela current and rejoins the gyre.
Explain how the circulation cells in the atmosphere and the associated surface winds assist in the transfer of energy between areas of surplus and deficit (8)
- Warm air rises at the Equator, travels in the upper atmosphere to 30° North and South of the Equator
- When the air cools, it becomes more dense and sinks.
- Some of this air returns as surface NE or SE trade winds to the Equator to form the Hadley Cell.
- The remainder of the air travels north over the surface as Westerlies to converge at about 60°North and South of the Equator with cold air at the Poles
- This convergence causes the air to rise, as the hot air makes the cold air from the poles warmer
- Some of this air flows in the upper atmosphere to the Poles where it cools when it meets with cold air from the polar regions
- This air cools and sinks to the surface, forming the Polar Cell.
- The remainder of this air in the upper atmosphere travels south and sinks at 30°North and South of the Equator to form the Ferrel Cell.
Explain the origin, nature and characteristics of the Tropical maritime and Tropical continental air masses (6)
Tropical Maritime Air Mass
• Origin: Ocean (Gulf of Guinea)
• Nature: Cold
• Characteristic: Contains a lot of moisture
Tropical Continental Air Mass
• Origin: Desert (Sahara Desert)
• Nature: Warm
• Characteristic: Dry
Describe and explain the variations of rainfall in West Africa (12)
- The South Westerly and North Easterly trade winds blow towards the equatorial low pressure, which is called the Inter Tropical Convergence Zone. (ITCZ)
- The ITCZ follows the overhead Sun, so it’s position in relation to West Africa varies throughout the year, resulting in variations in rainfall.
• In January, the ITCZ is in the South of West Africa.
- This results in cool, moist air from the Gulf on Guinea South of the ITCZ.
- This cool, moist air brings more rainfall to places such as Lagos.
- This also means that the warm, dry air from the Sahara Desert North of the ITCZ.
- This warm air brings dry weather to places such as Minna.
• In April, the ITCZ has moved north to Central West Africa
- This means that the previously dry Minna is now South of the ITCZ, bringing it rainfall from the moist Southern Westerly winds
- However places such as Agades are still North of the ITCZ, meaning there is still little rainfall there.
• In July, the ITCZ has moved further north to Northern West Africa.
- This means that the previously dry Agades is now South of the ITCZ, bringing it rainfall from the moist South Westerly winds.
- By this time of year, the ITCZ does not move any further North, so areas north of here are dry or desert.
• In October, the ITCZ moves South back to Central West Africa
- This means that the ITCZ moves below Minna, removing the moist air and rainfall.
- By the time the year finishes, the ITCZ moves back to the South of West Africa, where Lagos remains South of the ITCZ all year round, bringing it much rainfall.
Explain the physical factors which have led to changes in air temperature (10)
• Variations in Insolation
- Energy from the sun is not always the same
- It varies in cycles of approximately 11 years, and periods of increased solar energy are called sunspots
• Changes in Ocean Currents
- The North Atlantic Drift brings 30% of all Western Europe’s heat.
- Some years the current may vary in the distance it travels North, resulting in less heat being brought to Western Europe
- The currents may also vary in strength in some years, again resulting in differences in heat brought to Western Europe
• Volcanic eruptions
- These large eruptions add extra dust particles to the atmosphere, which absorb the suns radiation and lowers the world temperature
- If there are many volcanic eruptions at once, this can lower the worlds temperatures significantly
• Astronomical Changes
- The Earth’s orbit around the sun stretches, changing the worlds temperature depending on its distance from the sun
- The Earth’s tilt on the X-axis also changes a little, so changing the areas that receive the Sun overhead
- The Earth wobbles on its axis, so this changes the heat that different areas of the planet receive.
Explain the human factors which have led to changes in air temperature (10)
• Humans are putting more greenhouse gases into the atmosphere, especially carbon dioxide, methane and CFC's • Greenhouse gases increase temperature because they allow in Sun's heat energy but prevent heat from the Earth escaping back into space • Carbon dioxide is increasing due to: - Burning fossil fuels - Deforestation - Car Exhaust fumes • Methane is increasing due to: - More rice fields - More domesticated animals and animal dung - Belching cows • CFC's are increasing due to: - More aerosols being used - Use of solvents - Foam packaging
Explain the possible consequences of global warming throughout the world (10)
• Sea levels will rise
- More ice melting and warmer water expanding, resulting in flooding in costal cities, and more money needing to be spent on floor prevention and repair
• Glaciers will retreat
- This will result in an increase in meltwater, causing rivers such as the Rhine to flood more often
• More extreme weather
- Hurricanes increase in intensity, such as Katrina, and will result in mass migration away from danger areas
• Spread of tropical diseases
- More disease could be spread to Western countries, such as Malaria, resulting in more money spent of health services
• Areas become drier
- Crop fields reduce and famine occurs, resulting in even more poverty in developing countries
