Atmosphere - Physical

The atmosphere is the thin, gaseous layer that surrounds earth. It forms a small part of earth's mass (less than 0.1%), however it constantly interacts with the land and oceans[2] and involved with many ecosystem processes.

Quick facts

The thermosphere

is where auroras occur and satellites orbit, which is between 150km - 600km above the Earth's surface[1]

Physical components in the atmosphere

The atmosphere on earth has a number of layers. Starting at the ground, the layers are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The ionosphere extends from the mesosphere to the exosphere. Beyond the exosphere is outer space. The boundaries between atmospheric layers are not well defined, and change depending on latitude and season.

The troposphere starts at the earth's surface, and is the most dense layer, extending 8 to 14.5km above the surface. This layer contains almost all weather and contains the climate that creates conditions for life[1].

The stratosphere extends 50 km from the troposphere. This is where the ozone layer is contained and the layer which absorbs and scatters harmful ultraviolet radiation[1].

The mesosphere starts above the stratosphere and extends 85km high. Meteors burn up in this layer[1].

The thermosphere extends 600km from the mesosphere and this is where satellites occur, and auroras[1].

The ionosphere contains electrons and ionised atoms, and starts at the surface to the edge of space (about 965km) - which overlaps with the mesosphere and thermosphere. This layer is dynamic and changes size depending on solar radiation. The ionosphere is the link where interactions and processes between the sun and earth occur[1].

The exosphere is the upper limit of the atmosphere, extending 10,000km from the thermosphere.

Solar heat drives atmospheric circulation, and causes water in the oceans to evaporate, producing warm and humid air which rises into the atmosphere and forms clouds. Warm air can hold more moisture than cold air. The differences in temperature and density cause air in the atmosphere to move[2].

Warm air rising, creates a low pressure zone at the ground. Air from the surrounding area is sucked into the space left by the rising air. Air flows horizontally at the top of the troposphere, which is called advection. The air cools until it descends, and where it reaches the ground, it creates a high pressure zone. Air flowing from areas of high pressure to low pressure create winds. Air moving at the bases of the three major convection cells in each hemisphere north and south of the equator creates the global wind belts[2], and smaller pressure systems create localised winds that affect the weather and climate of a local area.

Convection in the atmosphere creates the planet’s weather. When warm air rises and cools in a low pressure zone, it may not be able to hold all the water it contains as vapor. Some water vapor may condense to form clouds or precipitation.

Wind patterns are influenced by a wide range of factors, from large-scale pressure patterns to the time of day and the nature of the surrounding terrain. Wind speed and direction are highly variable but there are sources available to predict wind:

• The Earth Wind Map shows, in real time, wind speed and direction across the earth using a 3D map.
• Windy.Com shows information on wind speed, gusts and direction across the world every six hours. It also collects temperature and rain information.
• WillyWeather uses information from the Bureau of Meteorology to show real-time wind speed and gusts. It also has historical information on speed and direction averages.
• The Bureau of Meteorology provides a static map of wind direction and speed. It also provides information on pressure, climate influences, humidity, sunlight and water.

Differences in moisture, density and temperature trigger weather events such as storms and cyclones where warm air confronts colder air.

Wind also generates ocean waves which drive many shoreline processes. Turbulent air moving over the ocean distorts the surface of the water, by depressing the surface when moving downward, and elevating the water's surface when moving upward (due to a decrease in pressure on the water's surface). The wind and changes in atmospheric pressure produce irregular and wavy surface to the ocean. The strength and direction of wind impacts the shape and power of ocean waves[2].

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References

1. ^ a b c d e f Data, MNASA (7 June 2018), 'About the Atmosphere: Background Information', My NASA Data. [online] Available at: https://mynasadata.larc.nasa.gov/basic-page/about-atmosphere-background-information [Accessed 5 September 2023].
2. ^ a b c d Hamblin, WK & Christiansen, EH (2001), Earth's dynamic systems, Prentice Hall, Upper Saddle River, NJ.

Last updated: 22 March 2013