The structure of the atmosphere

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The structure of the atmosphere

Structure of the atmosphere:

·         It is relatively thin but vital to support life on earth

·         The atmosphere is roughly 1000km thick, although most of it is in the lowest 40km above the earth’s surface

·         The atmosphere does not have a sharply defined outer edge; instead the air just becomes progressively thinner

·         The atmosphere is made up of gases

·         Influenced by the earth’s rotation and surface features, the atmosphere acts like a liquid twisting and turning in highly complex interconnected waves

·         The atmosphere has layers

o   Troposphere:

§  Warm earth heats the surface layers of the troposphere

o   Stratosphere:

§  Relatively high concentration of ozone absorbs UV radiation and increases temperature

o   Mesosphere:

§  Temperature gradually decreases with altitude

o   Thermosphere:

§  Temperature increases due to the absorption of high-energy UV and x-rays from the sun

The atmospheric heat budgets:

·         The driving force between our weather and indeed all life on earth is heat energy from the sun

·         The movement of heat in the atmosphere is called the atmospheric heat budget

·         The energy from the sun is called solar radiation

o   It arrives in the form of short-wave radiation

·         Not all radiation reaches the Earth some is:

o   Some is lost as it is scattered, absorbed and reflected by the atmosphere’s gases, liquids and solids

·         The solar radiation that does reach the Earth is called insolation

·         Some radiation is immediately reflected back into the atmosphere off white surface such as ice and snow

·         The reflectivity of a surface is called its albedo – the greater the reflectivity of a surface the higher the albedo

·         Heat is transferred back to the atmosphere from the Earth’s surface as terrestrial radiation

o   This takes the form of long-wave radiation

·         Heat transfers may involve processes such as conduction and convection

·         Conduction is the transfer of heat by contact with a substance whereas convection occurs when warm air rises, taking with it the energy that it stores

·         A further heat transfer involves latent heat

·         During evaporation water changes from a liquid to gas – the heat that is used during this process is stored as latent heat

·         When conduction takes place the gas is converted to water droplets and clouds releasing latent heat

·         Once in the atmosphere gases and liquids readily absorb the long-wave terrestrial radiation

·         This heats the lower atmosphere and is known as the greenhouse effect

·         Without this warm blanket surrounding the Earth it would be far too cold for life to exist

·         Some scientists believe that it is the increasing absorption of heat caused by emissions of gases such as carbon dioxide that lies behind the recent global warming trend



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