How do atmospheric circulations govern weather patterns and climate?

In this article, you will learn about global atmospheric circulation and how it creates different climate zones.

The Earth is governed by two main cycles: energy and water. Each has particular effects on local weather and long-term climate variability. The main driver of these cycles is solar radiation.

The relatively short waves of solar radiation entering the Earth’s atmosphere drive the energy and water cycles. Incoming solar radiation is taken up by the atmosphere, land and ocean, only to be emitted again as long-wave radiation: heat. This heat, in turn, provides energy for the processes of evaporation and evapotranspiration, which are key processes of the water cycle. The movement of energy in the form of heat and water transport, with energy being exchanged during phase changes between liquid water and water vapour, drive the global atmospheric circulation, Figure 1.

Figure 1: Atmospheric Global Circulation, by Kaidor, licensed under CC BY-SA 3.0 (Click to expand)

Trade winds in the Northern Hemisphere blow from East to West, carrying the air to the Intertropical Convergence Zone. There, the air mass becomes warmer. As the air rises, it travels towards the North and South subtropics. Then the air cools down and descends to the surface of the Earth. This global circulation affects the weather of the planet. It creates warm-rising winds, which lead to areas of frequent rainfall in the tropics. And cool-descending winds that create areas of dryness, like the deserts. A graphical representation is to the right side of the Globe in Figure 1. Note that the inclination of the Earth leads to seasonality. This causes the system to displace southward in December to March and northward in June to September.

Up next

In the following articles, we will introduce the weather and climate systems to be able to differentiate them.