the atmospheric system
The atmosphere is a mixture of transparent gases held to the earth by gravitational force.
The atmosphere predominantly consists of 78.09% Nitrogen and 20.95% Oxygen, other gases include:
Due to gravity and compression, most of the atmosphere is close to the Earth's surface. It is a vertical structure consisting of:
This is shown opposite.
The atmosphere predominantly consists of 78.09% Nitrogen and 20.95% Oxygen, other gases include:
- Carbon dioxide,
- Hydrogen,
- Helium
- Methane.
Due to gravity and compression, most of the atmosphere is close to the Earth's surface. It is a vertical structure consisting of:
- Troposphere
- Tropopause
- Stratosphere
- Mesosphere
- Mesopause
- Thermosphere
This is shown opposite.
Atmospheric heat budget
Solar radiation or INSOLATION is the energy source that drives the atmosphere. This radiation varies around the globe and through the seasons.
The incoming radiation is roughly constant at 342 W/m2, the SOLAR CONSTANT. The total values of
incoming and outgoing radiation is usually balanced, this is the GLOBAL ENERGY BUDGET.
Incoming radiation = Short Wave
Outgoing radiation = Long Wave
Short wave radiation is absorbed by water vapour, carbon dioxide and the Earth’s surface before being re-radiated as long wave radiation. This is the GREENHOUSE EFFECT. This is a natural process which maintains Earth's habitable global temperature.
The amount of solar energy received (the receipt) from the sun varies, with the impact of this explaining why there is less insolation receipt in the polar regions compared to the tropics.
There are spatial and temporal variations in the amount of insolation received at the earth’s surface, these include:
Solar radiation or INSOLATION is the energy source that drives the atmosphere. This radiation varies around the globe and through the seasons.
The incoming radiation is roughly constant at 342 W/m2, the SOLAR CONSTANT. The total values of
incoming and outgoing radiation is usually balanced, this is the GLOBAL ENERGY BUDGET.
Incoming radiation = Short Wave
Outgoing radiation = Long Wave
Short wave radiation is absorbed by water vapour, carbon dioxide and the Earth’s surface before being re-radiated as long wave radiation. This is the GREENHOUSE EFFECT. This is a natural process which maintains Earth's habitable global temperature.
The amount of solar energy received (the receipt) from the sun varies, with the impact of this explaining why there is less insolation receipt in the polar regions compared to the tropics.
There are spatial and temporal variations in the amount of insolation received at the earth’s surface, these include:
- The Solar Constant- Sun spot activity can vary this, and changes can be linked to long term climate change.
- Angle of the Sun- High-angle sun in the tropics is more intense than low-angle sun at the poles.
- Length of the day/night- This varies with the position of the overhead sun. The northern hemisphere has longer days and shorter nights in summer which increased the insolation received. The reverse of this happens in the winter.
- Aspect- In the northern hemisphere, south-facing slopes receive more direct insolation that north-facing ones
- Atmosphere - Water vapour and carbon dioxide absorbs incoming radiation
- Albedo- This is a measure of the percentage of reflected incoming energy off different surfaces, for example snow, grass and ice. different albedos effect the total amount of received solar energy.
- Altitude of the sun- The concentration of heating intensity varies with the angle of the suns rays to the surface and thickness of the atmosphere it passes through .
- Seasons- The seasons effect the effect of the altitude of the sun and it effects the length of the day changing the amount of solar receipt.
- Cloud cover- The greater the cloud cover the more solar radiation is reflected. clouds also retain heat that would have been lost by radiation from earth reducing the daily temperature range.
- Land and sea- The different specific heats of land and water varies the storage and release of heat. Continentality summarises the effect of difference in heating and cooling of sea and land areas. there are greater seasonal extremes of temperature over land than sea.
- Altitude- The higher the altitude the greater input of solar radiation because there is less atmosphere to pass through. increased cloud cover however can counteract this.
Transfer of Heat
Heat energy is transferred by:
Heat energy is transferred by:
- Radiation, both short and long wave. Radiation can be absorbed by gases and/or scattered due to contact with aerosols (small particles), water droplets or gas molecules.
- Conduction, where heat passes through matter. This is more important to surface heat as air is a poor conductor at atmospheric level.
- Convection, this circulates heat through liquids and gases. this is the main means of atmospheric heat transfer. There are two forms of energy transfer: SENSIBLE HEAT and LATENT HEAT.
Energy exchange
There are two energy transfers needed to balance out polar and tropical regions:
Temperature patterns
Two main factors affect the spatial and seasonal patterns of temperatures and of temperature ranges and anomalies:
There are two energy transfers needed to balance out polar and tropical regions:
- Horizontal - Through winds and ocean currents. Anticylcones and depressions are important in this transfer
- Vertical- Through convection, conduction, radiation, release of sensible heat from condensatin and latent heat transfer after evaporation
Temperature patterns
Two main factors affect the spatial and seasonal patterns of temperatures and of temperature ranges and anomalies:
- Energy transfers: winds and ocean currents
- Variations in solar energy received at the surface: latitude, altitude, land and sea distribution