INSOLATION
This stands for INcoming SOLar radiATION
Insolation controls the vegetation which grows in the area, and therefore the environment that develops. It affects climate, the development of soils, the rate of weathering, the ability to develop agriculture, and therefore population density.
Sun's energy powers all natural systems and cycles.
Sun's energy is produced by nuclear fusion, which gives off electromagnetic radiation.
Travels at the speed of light and takes around 8 minutes to travel the 93 million or so miles to the Earth
Light is mainly in the Ultra Violet wavelengths and visible light, with a smaller amount of Infra Red.
Almost all shortwave due to Wien's Law: wavelength of energy is inversely proportional to temperature of radiating body
Solar constant is the near constant (varies in cycles - sun spot activity) amount of energy received at the edge of the atmosphere: 2 langleys per square centimetre per minute
Remember that the temperature of the earth is very finely balanced. A drop of just 2 to 3 degrees Celsius would see ice sheets start to grow and move across the Northern hemisphere. This is because small changes in temperature change the way that water behaves.
The temperature of the surface is the result of 3 main factors:
Insolation: the solar power per unit area at the top of the atmosphere as measured perpendicular to the solar beam. The amount that we receive is affected by our distance from it, and the luminosity of the sun itself.
Albedo: planetary albedo is the fraction of the insolation reflected back into space
The atmosphere's optical depth: earth's light absorption and re-emission characteristics (basically, this is greater nearer the poles than the equator because of the angle of tilt of the earth's axis) - think of the atmosphere as being like a pane of glass (or rather, several panes of glass) As the light passes through each pane, some of it is absorbed, so after passing through several panes it is not as bright. The modern atmosphere's effective optical depth is about 0.6
Image sourced by GOOGLE image search.
The 3 factors above can be affected by human activities (this is SYNOPTIC type information...)
Earth's Heat Budget: need to have a reproducible diagram showing the destination of the heat that is received at the outer edge of the atmosphere - this has to balance each year, or the earth would warm up / cool down. Energy enters and leaves the earth almost entirely as light. (Remember that light is given off as a wave breaks!)
The earth is said to be in thermal EQUILIBRIUM.
The values given below may vary depending on which textbook you read....
100 UNITS: total insolation received at the top of the atmosphere
Albedo = 30: insolation reflected back into space without being absorbed or altered
Absorbed by earth's surface = 50
Absorbed by earth's atmosphere = 20, of which 3 is absorbed by the Ozone layer
Outgoing radiation lost to space = 100 units
Longwave radiation lost directly to space = 12
Longwave radiation emitted to space by the atmosphere = 58
Longwave radiation transferred from earth's surface to the atmosphere through the greenhouse effect = 8
Heat transferred from earth's surface to atmosphere through latent heat in water vapour = 23
Factors which affect DIFFERENTIAL HEATING:
Latitudinal differences: Angle of Incidence
Day length
Atmospheric obstruction
Latitudinal radiation balance
Land and water contrasts