| The interaction between the heat from the sun | | | | trade winds. By the time it reaches the equator, it |
| and the earth's atmosphere is greatly responsible | | | | dies out and this was called the doldrums by |
| for the weather of the world. The unequal heating | | | | sailors. |
| of the earth and the atmosphere's tendency to | | | | Thus we can see that the global circulation of air |
| reach equilibrium forces the movement of large | | | | is to a large extent a cause of the rise of air in |
| mass of air. This causes changes in the weather | | | | the tropics, sinking of the same in between the |
| condition. | | | | 30 degrees north and south latitude and also the |
| The tilt in the earth's axis causes the seasonal | | | | eventual flowing back of it to the equator. This |
| variations as different parts of the earth receives | | | | whole process was first observed by English |
| varied amount of the sunrays everyday. The | | | | scientist George Hadley and thus it gets its name |
| Tropical Zone between 23.5 degrees north and | | | | as the Hadley cells. |
| 23.5 degrees south receives maximum heat | | | | The whole of the rising equatorial wind do not sink |
| throughout the year. This effects convection. This | | | | in the 30 degrees' zone. Some continues to flow |
| convection causes the hot air to rise up, form a | | | | till they reach the poles. They meet the polar air |
| low pressure and come down again as rainfall. | | | | at 60 degrees north and south. This zone is called |
| Until it reaches the tropopause (the juncture of | | | | the polar fronts. From here the warmer air |
| the stratosphere and the troposphere) the hot air | | | | moves towards the 30 degrees' area and this |
| keeps moving up. It cannot cross the tropopause. | | | | was first observed by William Ferrel in 1856. Thus |
| It spreads towards the pole and then cools and | | | | this process earns its name: the Ferrel cells. |
| sinks down generally in between the 30 degrees | | | | There are some air that rises at the 60 degree |
| north and south. The sinking air produces a high | | | | and flows towards the 60 degrees north and |
| pressure belt which causes dry and sunny climate. | | | | south zone. This is quite a weak process and is |
| The deserts on the earth are located mostly in | | | | popularly called the polar Hadley cells. |
| these zones. | | | | So next time you are enjoying your vacation to |
| In the zone between the 30 degrees north and | | | | Villajoyosa and Costa Blanca you can understand |
| south latitudes the sinking air displaces a | | | | why the weather in those places is so excellent |
| considerable mass of air that was already there. | | | | at almost all times of the year. |
| Some of it moves towards the equatorial area as | | | | |