ARTICLE INDEX:
We can gain an understanding of how global (or planetary) circulation works by developing two simplified graphical models of processes that produce this system. The first model will be founded on the following simplifying assumptions:
- The Earth is not rotating in space.
- The Earth's surface is composed of similar materials.
- The global reception of solar insolation and outgoing longwave radiation cause a temperature gradient of hotter air at the equator and colder air at the poles.
Based on these assumptions, air circulation on the Earth should approximate the patterns shown on Figure 1. In this illustration, each hemisphere contains one three-dimensional circulation cell.
Figure 1 - Simplified one-cell global air circulation patterns.
As described in the diagram above, surface air flow is from the poles to the equator. When the air reaches the equator, it is lifted vertically by the processes of convection and convergence. When it reaches the top of the troposphere, it begins to flow once again horizontally. However, the direction of flow is now from the equator to the poles. At the poles, the air in the upper atmosphere then descends to the Earth's surface to complete the cycle of flow.
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