6.1 Introduction to the Atmosphere Flashcards
Atmosphere definition
a dynamic system (with inputs, outputs, flows and storages) that has undergone changes throughout geological time.
Atmosphere Inputs
- Water (evaporation and transpiration)
- CO2, SO4 and NO2 from combustion
- Volcanic ash
- Solar radiation
- oxygen through photosynthesis
- aerosols
Atmosphere outputs
- precipitation
- solar radiation
- oxygen for respiration
- CO2 for photosynthesis
the composition of the atmosphere: nitrogen
78%
- importance for weather and climate: mainly passive
- needed for plant growth
the composition of the atmosphere: oxygen
21%
- importance for weather and climate: mainly passive
- produced by photosynthesis
- reduced by deforestation
- needed for animal life
the composition of the atmosphere: argon
0.9%
the composition of the atmosphere: carbon dioxide
0.04%
importance for weather and climate:
- absorbs long wave radiation from earth and therefore contributes to natural greenhouse effect
- increases due to human activity is a major cause of global warming
- used by plants for photosynthesis
- increased by burning fossil fuels and deforestation
the composition of the atmosphere: water vapour
0.2 - 4.0%
importance for weather and climate:
- source of cloud formation and percipitation
- reflects/absorbs incoming radiation
- keeps global temp. constant
- provides majority of natural greenhouse effect
- essential for life
- can be stored as snow or ice
Atmosphere levels (top to bottom) TMST
- thermosphere
- mesosphere
- stratosphere
- troposphere
Troposphere
- most weather processes happen here
- fall in temperature with height as atmosphere thins
Mesosphere
- Temperature declines with height
- Coldest part of the atmosphere.
- density prevents absorption of energy
Stratosphere
- lacks dust and water vapour
- stable
- thin
- increase in temp with height is due to absorption of solar radiation
- Ozone layer at the top of the stratosphere
Thermosphere
- virtual vacuum
- rise in absorbed energy due to energised short wave radiation
Albedo definition
a measure of the reflectivity of a surface.
Albedo effect
when applied to the Earth is a measure of how much of the Sun’s energy is reflected back into space
About how much of incoming solar radition is reflected back into space?
about 30% (shortwave radiation)
What is the greenhouse effect
- shortwave radiation travels from the Sun to the Earth
- some is reflected by Earth and the atmopshere
- most radiation is absorbed by the Earth’s surface and warms it
- infrared energy (longwave radiation) is radiated from the Earth’s surface
- some of the infrared energy passes through the atmosphere, some is absorbed and re-radiated in all directions by greenhouse gas molecules, warming the Earth and the lower atmosphere.
Discuss the role of the albedo effect from clouds in regulating global average temperature.
- Albedo (in this context) = the proportion of incoming solar radiation reflected by a surface.
- Low, thick clouds (e.g. stratus, stratocumulus) have high albedo (~0.7–0.9) and reflect a large amount of solar radiation, leading to cooling of Earth’s surface.
- High, thin clouds (e.g. cirrus) have low albedo (~0.1–0.3) but are located high in the atmosphere and are efficient at trapping outgoing longwave (infrared) radiation, + reemitting in all directions including down to earth, contributing to warming.
- Clouds reflect visible light effectively, appearing white due to wavelength-independent scattering—this makes albedo relatively constant across the visible spectrum.
- The net effect of clouds on global temperature depends on cloud type, altitude, thickness, and extent:
→ Low clouds → net cooling.
→ High clouds → net warming. - Clouds play a dual role in regulating climate:
→ Reflecting incoming shortwave radiation (albedo effect)
→ Absorbing and re-emitting outgoing longwave radiation (greenhouse effect)
Outline the role of the greenhouse effect in regulating temperature on Earth
- The greenhouse effect is a natural process that helps regulate Earth’s temperature.
- Certain gases like CO₂, CH₄, N₂O, and H₂O vapour allow shortwave solar radiation to pass through the atmosphere.
- Earth’s surface absorbs this energy and re-emits it as longwave (infrared) radiation.
- Greenhouse gases absorb and re-emit this radiation, trapping heat in the atmosphere.
- Without this effect, Earth’s average temperature would be around 33°C colder, making it uninhabitable.
- The greenhouse effect is essential for maintaining stable climates and supporting life.
how do humans impact the atmospheric composition?
through altering inputs and outputs of the system
what is the enhanced greenhouse effect?
the anthropocentric/human induced global warming as a result of increased use of greenhouse gases
main human activities releasing greenhouse gases/enhancing greenhouse effect
- burning fossil fuels (coal, oil gas) → releasing co2
- deforistation → takes away co2 store → releases more co2 into atmosphere
- increased intensive cattle farming = increased methane levels (cows digest grass via fermentatoin & anaerobic bacteria in their gut → methane as waste)
- fertiliserin agricultural systems → higher nitrous oxide concentration when fertilisers break down
GHG in the atmosphere
water vapour, co2, methane, nitrous oxide, CFCs and HCFC
Atmosphere processes
- respiration
- photosynthesis
- percipitation
- dry deposition
cumulus clouds
low, fair weather, 0.9 albedo
stratus clouds
dense, low-lying, light percipitation, 0.6 albedo
