The Atmosphere Flashcards
What is the approximate composition of the atmosphere?
-(Dry) Fixed gases (below 80km)
1) Nitrogen (78%)
2) Oxygen (21%)
3) Argon (1%)
Carbon Dioxide (422ppm and growing)
-Variable
1) Water vapour (0-4%)
2) Ozone (0.01ppm-10ppm)
3) Aerosols
How does pressure vary with height in the atmosphere?
It exponentially decreases.
Describe the vertical composition of the atmosphere.
1) Troposphere (0-10km)
-Contains ~75% of atmospheric mass.
-Weather, clouds, and turbulence occur here.
2) Stratosphere (10-50km)
-Contains the ozone layer (~20-30 km), which absorbs harmful ultraviolet (UV) radiation.
-Calm and stable, minimal turbulence.
3) Mesosphere (50-85km)
-Meteors burn up in this layer.
-Mesopause: Coldest region, boundary between mesosphere and thermosphere.
4) Thermosphere (85km+)
-Contains the ionosphere (partially ionized gases), crucial for radio wave transmission.
-Spacecraft and satellites orbit here.
-Auroras occur due to interaction of solar wind with charged particles.
Explain why the temperature profile of the atmosphere has that structure.
Troposphere: Temperature decreases with altitude.
Reason: Surface heating from solar radiation. (Greenhouse effect). Cools due to adiabatic expansion.
Stratosphere: Temperature increases with altitude.
Reason: Absorption of ultraviolet (UV) radiation by the ozone layer.
Mesosphere: Temperature decreases with altitude.
Reason: Lack of heat absorption and radiative cooling.
Thermosphere: Temperature increases with altitude.
Reason: Absorption of high-energy solar radiation.
Explain how the Earth maintains radiative equilibrium.
Earth maintains radiative equilibrium by balancing absorbed solar radiation with emitted infrared radiation.
The greenhouse effect regulates heat retention (adding 33 degrees to global temps.), while atmospheric and oceanic circulation redistribute energy.
Compare the Earth’s atmosphere to those on other terrestrial planets in the Solar System.
-Without an atmosphere there would be wide swings between day and night.
- No protection from harmful radiation
-The atmosphere transfers energy from the tropic to the poles.
-Provides weather.
-Controls the climate.
Explain the changes that unsaturated air parcels undergo when being displaced vertically.
1) Adiabatic Cooling: As the parcel rises, it expands because the pressure decreases. Since no heat is exchanged the parcel’s temperature decreases. The rate of temperature decrease is called the dry adiabatic lapse rate (10°C per kilometre).
2) No condensation: Since the air is unsaturated, the water vapor in the air does not condense. This means there’s no latent heat released during the vertical displacement.
3) Decreasing Relative Humidity: As the parcel rises and cools, its relative humidity increases, but it will not reach 100% unless the temperature drops to the dew point. If the parcel rises far enough, the relative humidity will reach 100% when it reaches its dew point.
Explain the changes that saturated air parcels undergo when being displaced vertically.
1) Adiabatic Cooling with Condensation: As the parcel rises, it expands due to the decrease in pressure. However, the cooling rate for a saturated parcel is slower than the DALR. This is because as the air cools and the water vapor condenses into liquid water and releases latent heat, which counteracts the cooling. This rate of cooling is known as the moist adiabatic lapse rate (4°C-6°C per kilometre).
2) Latent Heat Release: Condensation releases latent heat into the air parcel, providing additional energy and reducing the rate of cooling. The release of latent heat slows down the temperature decrease compared to an unsaturated air parcel.
3) Saturation is Maintained: Throughout the vertical displacement, the air parcel remains saturated. As it rises and cools, condensation continues, and the moisture content does not decrease unless the parcel begins to lose moisture or cools sufficiently for the relative humidity to drop below 100%.
Define saturation.
Saturation refers to the state in which air contains the maximum amount of water vapor it can hold at a specific temperature and pressure.
Define latent heat.
Latent heat refers to the heat energy absorbed or released by a substance during a phase change.
Explain the Earth’s general circulation.
Equator: The region around the equator is where the Sun’s rays are most direct, causing warm air to rise. ITCZ is located here where trade winds meet, and clouds frequently form, leading to heavy rainfall.
Hadley Cells: In the tropics, warm air rises near the equator and moves toward the poles. As it cools, it sinks around 30° latitude in both hemispheres, creating areas of high pressure. These descending air masses lead to dry regions and are known as the subtropical highs.
Trade Winds: In the tropics, winds blow from the east toward the equator, driven by the Coriolis effect. These are called trade winds.
Ferrel Cells: Between 30° and 60° latitude, air moves in the opposite direction of the Hadley cells. Warm air from the tropics moves toward the poles at the surface, while cooler air moves toward the equator aloft.
Westerlies: In the Ferrel cells, winds blow from the west to the east in both hemispheres.
Polar Cells: In the polar regions, cold air sinks and flows toward the equator, creating the polar cells, where air moves from high to low latitudes.
Polar Easterlies: In the polar regions, winds move from east to west.
Polar Fronts: This is the boundary between the cold polar air and the warmer air of the mid-latitudes, where most of the Earth’s storm systems occur.
