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Climate zones

Climate zones are areas with distinct climate, which occur in east-west direction around the earth, and can be classified using different climatic parameters. Generally, the climate zones are belt-shaped, and circular around the Poles. In some areas, climate zones  can be interrupted by mountains or oceans (see picture and world temperature maps). 


Climate zones

The solar radiation reaches the ground at different parts of the earth with different angles. At the equator meet, sunlight reaches the ground almost perpendicularly, whilst at the poles, the angle of the sun is lower or even under the horizon during the  polar night .
During the seasons, the position of the sun to the earth and thus the angle of incidence of the sunlight also change. The angle of the sun at noon varies from perpendicular (90°) within the tropics up to horizontal (0° = sun does not or only partially appear on the horizon) within the polar circle.
Thus, the sunlight warms up thus the earth around the equator much more strongly than at the poles. Due to temperature differences caused by the differences in radiation, recurring climatic conditions develop, such as winter and summer. These conditions are characterised by a certain amount of precipitation in the summer, or a certain average air temperature.
Different climatic conditions, which arise regularly in certain areas, are summarized and described in climate zones.

Tageslaenge 800px-en
Angle of sunlight incidence on earth. Author: Thomas Steiner.

Climate zones

There are 4 major climate zones:
  • Tropical zone from 0°–23,5° (between the tropics)
  • In the regions between the equator and the tropics (Equatorial region) the Solar radiation reaches the ground nearly vertically at noontime during almost the entire year. Thereby, it is very warm in these regions. Through the high temperatures, more water evaporates, so that the air is often moist. The resulting frequent and dense cloud cover reduces the effect of solar radiation on ground temperature .

  • Subtropics from 23,5°–40°
  • The subtropics receive the highest radiation in the summer, since the sun's angle at noon is almost vertical to the earth, whilst the cloud cover is relatively thin. These regions receive less moisture (see Trade winds), and that increases the effect of radiation. Therefore,  most of the deserts in the world are situated in this zone. In the winter,  the radiation in these regions decreases significantly, and it can be temporarily very cool and moist .

  • Temperate Zone from 40°–60°
  • In the temperate zone, the solar radiation arrives at a smaller angle, and the average temperatures here are much cooler than in the subtropics. The seasons and daylength differ significantly in the course of a year. The climate is characterised by less frequent extremes, a more regular distribution of the precipitation over the year and a longer Vegetation period - therefore the tame "temperate".

  • Cold Zone from 60°–90°
  • The polar areas between 60° latitude and the poles receive least heat through solar radiation, since the sun has a very flat angle to the ground. Because of the changes of the earth axis angle to the sun, the daylength  varies most in this zone. In the summer, polar days occur. The Vegetation  is only possible during few months per year and even then often sparsely. The conditions for life in these regions are very hard.

The characteristics of the climate zones change with large altitude differences within a small area , as e.g. in  mountain areas, since the temperatures decrease rapidly with the altitude , changing the climate compared to valleys.