Global air circulation. Artwork of the Earth illustrating the three cell model of global air circulation. In this model, atmospheric circulation occurs in convection cells located at polar, mid-latitude and tropical latitudes. They are known as the polar, Ferrel and Hadley cells, respectively. The arrows within these cells indicate the flow of warm air (red) and cool air (blue). The effect of the Earth's rotation causes the flow around the cells to be deflected, giving rise to three main wind patterns, indicated by thick arrows. These are: the polar easterlies (blue), the prevailing westerlies (green) and the tropical easterlies or trade winds (orange).