Earth's atmosphere Flashcards
define atmosphere
a layer of gases surrounding Earth or another planet held in place by the planet’s gravity
air is …
compressible and one can determine its density
where is the atmosphere at its densest and lowest?
densest - sea level
higher altitudes- lower
why is it important for life on earth ?
1) it absorbs the sun’s energy
2) recycles water and other chemicals
3) moderates climate
4) protects life from high energy radiation
properties change with height
thinner with height with no definite boundary between atmosphere and outerspace
oxygen decreases with height
Name the 5 atmospheric layers
1) the troposphere
2) stratosphere
3) mesosphere
4) thermosphere
5) exosphere
the troposhpere
1) the air we breathe
2) extends to 15 km high
3) temperature falls with altitude of -50 degrees Celsius
4) all weather is in this region
5) tropopause - separates the troposphere from stratosphere
the stratosphere
1) starts above the troposphere and extends 50km above Earth’s surface
2) less water vapour and less dense
3) temperature increases with height -3 degrees Celsius =absorption or radiation
4) ozone layer - absorbs and scatters uv rays
5) the stratopause separates from the mesosphere
The mesosphere
1) Just above the stratosphere -extents to 85km
2) temperature falls with increases altitude to about -90 degrees celsius
3) mesospause separates the mesosphere from the thermosphere
the thermosphere
1) extends to an altitude of 600 km
2) highly ionized with gases
3) temperatures increasing with altitude up to 1700 degrees celsius
the exosphere
1) outermost layer
2) extremely dilute gases ; hydrogen and helium with atoms escaping
3) sometimes considered as the interface between atmosphere and space as it gradually merges into space with no clear boundary
composition of the atmosphere
nitrogen oxygen carbon dioxide other gases water vapour is also present but varies because warmer air holds more
solar budget
The total solar energy received by Earth and the total energy radiated back to space must be equal because Earth’s overall temperature changes
solar constant
the amount of solar energy received at the top of Earth’s atmosphere (varies due to slight changes in distance between earth and sun
where does the sun’s energy go ?
Half of it is absorbed by the atmospheric gases(ozone and water vapour ) or reflected and scattered by clouds and dust - the rest is absorbed by Earth’s surface
Global circulation
Energy transfer with the earth’s atmosphere system - not all parts of earth received the same amount of solar energy ex the poles receive far less than the equator
how is heat transferred?
heat transfers form warmer to colder areas - the uneven distribution of heat produces convention currents which redistribute heat energy - these convention currents are experienced as winds and ocean currents (otherwise the tropics would get warmer and the poles would get colder )
how does it happen exactly ( heat transfer )
intense heating at the equatorial region initiates convention currents - this warm air rises at troposphere - flows horizontally towards poles and eventually returning to earth’s surface (30 north and 30 south )
this massive convention current is called the Hadley Cell
the 2 other cells
the polar cell and the Ferrel cell
The albedo
the proportion of incident light that is reflected by a surface - depends on the albedo of the surface receiving sunlight
what affects the albedo ?
1) different colour and texture - clean snow ( high reflectivity ) - forest ( low reflectivity )
clouds - high reflectivity
what happens if the planet’s albedo changes
increases- cooling of global temperature
decreases - warmer planet
The greenhouse effect
incoming and outgoing radiation balance out however they have different properties
1) the incoming radiation is a mixture of ultraviolet , visible and infra-red radiation- these radiation are of a short wavelength
2) Earth radiates back heat with a longer wavelength of infra-red radiation
3) Earth’s atmosphere contain gases that absorb some of this thermal radiation emitted - re-radiate energy in all direction - warming effect - greenhouse effect
Greenhouse gas
a gas that absorbs thermal infrared radiation and therefore contributes to the greenhouse effect
Greenhouse effect definition -
the warming effect of the atmosphere that occurs when infrared energy is emitted by earth’s surface is absorbed by gases in atmosphere - a fundamental natural phenomenon to life on earth - temperature which sustains life
name the greenhouse gases
1) water vapour
2) carbon dioxide
3) methane
4) ozone
5) nitrous oxide
6) chlorofluorocarbons
sources of greenhouse gases
landfills- methane emissions
deforestation - a large amount of carbon dioxide
combustion of fossil fuels - carbon dioxide
The ozone layer
- the stratosphere zone -
protects life from the damaging uv rays - the ozone is constantly created and destroyed but because of human activity the increasing rate of destruction is resulting in the disruption of balance - will lead to ozone depletion
