Atmosphere The energy budget

AtmosphereThe energy budget “Explain why there is a surplus of solar energy in tropical latitudes and a deficit towards the poles” This graph shows that at the equator the amount of energy received from the sun, insolation, is much greater than at higher latitudes ie the poles.

AtmosphereThe energy budget At the equator the sun’s rays strike vertically, at right angles i.e. from directly overhead. This means that they transfer much more of their energy to the Earth, causing more heating. Angle of the sun’s rays (1) Due to the curvature of the Earth, however, at the poles less energy from the light rays is successfully transferred to the ground because the angle (of incidence) is much greater.

AtmosphereThe energy budget The angle at which the sun’s rays strike the Earth also affect the area to be heated by those light rays. Angle of the sun’s rays (2) At the Equator isolation is concentrated on a relatively small area, thus making the heating there more effective. While at the Poles the same amount of light rays are spread over a much wider area, reducing the effect of the heating at those higher latitudes.

AtmosphereThe energy budget Atmosphere to be passed through At the Equator light from the sun passes through a relatively narrow band of the atmosphere before it gets to the ground. This means that most of it will get through without being absorbed by dust particles (dark) or reflected by clouds (light). At the Poles however, there is more of the atmosphere for light to get through. This increases the chances of it being absorbed or reflected and thus not reaching the ground. The distance AB < XY YX BA

AtmosphereThe energy budget Land surface and albedo effect The land surface of the Earth at the equator is dark equatorial rainforests. This absorbs the light from the sun well and so heats up the atmosphere above. At the Poles however the land surface tends to be lighter in colour eg Tundra or ice caps. These are more reflective and so don’t heat up as much, meaning less heating of the atmosphere here.

AtmosphereThe energy budget Latitudes effect on the length of the day The Equatorial areas of the world receive around 12 hours of sunshine all year round. Due to the tilt of the Earth’s axis however the Poles find themselves in almost total darkness for up to 3 months as they face away from the sun according to the seasons. This dramatically reduces the solar energy reaching the poles but maintains a high level throughout the year for low latitudes. At the Equator there is a steady amount of insolation throughout the year. At the Poles there are parts of the year with no insolation at all.

AtmosphereThe energy budget Latitudes effect on the length of the day This is the situation during winter in the northern hemisphere (November- January). The days are shorter, but at the Pole itself there is complete darkness – at no point in the Earth’s daily rotation does the North Pole face the sun. The equator however always faces the sun, vastly increasing its insolation in comparison with the pole.

AtmosphereThe energy budget 2006

AtmosphereThe energy budget 2005

AtmosphereThe energy budget 2002

AtmosphereThe energy budget 1997

AtmosphereThe energy budget Latitudes effect on the length of the day The

AtmosphereThe energy budget

AtmosphereThe energy budget