6.1 Introduction to the Atmosphere Flashcards
What is the “atmosphere”?
- Thin envelope of gases that surrounds the Earth
- Arranged in different layers
- Wind and weather
What is the “atmosphere” compromised of?
- Gases (nitrogen, oxygen, carbon dioxide)
- Small solid particles (dust, pollen, ash)
- Water
How is the earth a “dynamic” system?
- Atmospheric system is driven by the Sun.
- Natural dynamic equilibrium of processes maintains the average composition of the atmosphere at levels that only change significantly over very long timescales
- Most important = photosynthesis and respiration
What was earth’s early atmosphere like?
- Earth atmosphere formed by gases given out by volcanos
- Mostly CO2 with little or no oxygen
- Most of the water vapour condensed and formed oceans
- Smaller proportions of water vapour, ammonia and methane
What are some of the human activities impacting the atmosphere?
The proportion of greenhouses gases in the atmosphere is increasing due to:
- Burning fossil fuels
- Deforestation releasing CO2 and reduction in forest cover reducing CO2 taken out of atmosphere
- Intensive cattle farming releasing methane
- Rice farming in paddy fields releasing methane
- Fertiliser use releasing nitrous oxide
What is a “lapse rate”
Rate at which temperature declines with increasing altitude in the troposphere
How does the “Temperate profile of the atmosphere” look like?
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What is the “Troposphere”?
This is the layer closest to the earth’s surface and includes where we live. It extends up to about 10km above sea level and is where:
- The earth surface absorbs heat from the sun. The warm earth then heats the atmosphere through conduction. The troposphere is warmest near the earth surface with temperature declining by around 6.5°C per kilometre.
- Most of the atmospheric mass is found. This includes nearly all the water vapour, clouds and pollutants.
- Most of our weather occurs.
- Humans and other organisms have most interaction e.g. through exchange of gases or through introduction of pollutants.
- The greenhouse effect occurs and helps to regulate the temperature of the earth.
What is the “Stratosphere”?
–> extends from 10km to 50km above sea level
- Stratospheric ozone absorbs ultra violet radiation from the sun. Temperature is constant at about -60°C in the lower part of the stratosphere, which is shielded by the ozone layer but then increases with altitude.
- The air is dry.
- Winds increase with height.
What is the “Mesosphere”?
This layer ranges from about 50 to 80km and is where:
- Without the presence of ozone or other particulates to absorb UV radiation, the temperature declines with height. It is the coldest part of the atmosphere with temperatures falling to -100°C.
- There are strong winds with speeds up to around 3,000km/h.
What is the “Thermosphere”?
This layer extends beyond about 80km to between 500km and 1,000km. Within the thermosphere:
- UV and X-radiation from the sun is absorbed which breaks apart molecules into atoms (oxygen, nitrogen and helium atoms are the main components in the upper thermosphere).
- The temperature increases with height and can reach beyond 2,000°C. This heat can cause the layer to expand causing variation in depth overtime from 500 to 1,000km.
What is the greenhouse effect?
(Natural effect that maintains temperatures suitable for life on earth)
- Some solar radiation is reflected by Earth and the atmosphere (some is absorbed by the earth and warms it)
- Some of the infrared radiation passes through the atmosphere,
HOWEVER:
Some is absorbed by greenhouse gases and re-emitted in all directions by the atmosphere. The effect of this is to warm Earth’s surface and the lower atmosphere.
What are some of the roles of the greenhouse effect?
- Maintain mean global temperature
- Normal and necessary condition for life on Earth
- Allow short wavelengths of radiation (visible light and UV) to pass through the earth’s surface
- Trap longer wavelengths such as infrared radiation
