Question

7. The Professor and gallant crew don't know exactly where their island is, but it is near the equator and they have been marooned long enough to have experienced changes in weather patterns due to the ENSO. The Professor and the Skipper have been monitoring rainfall and have noticed that there is a cycle of 3-5 years between wetter and drier conditions. Explain why there should be a regular oscillation between wetter and drier conditions in terms of the strength of the easterly trade winds and their effect on the location of maximum heating of the Intertropical Convergence Zone. (6)

Answer 1

Intertropical convergence zone is the place where the southern and northern tropical winds are comes together to produced low pressure area. This area circles the earth and it is near equator.

The intertropical convergence zone shows the dry and wet season instead of summer and winter. These periods are depending on the strength of the trade wind. Trade wind means the wind flows towards the equator and have effect of Coriolis force. At ITCZ both winds that is northeast and Southwest winds comes together and due to there strength the pressure is changes. When ITCZ is to the south of equator the North East wind prevail over Nigeria, produces the dry season and when Southwest wind prevail, ITCZ is shifted towards the North and produces the wet season but in between wet and dry pressure is low which causes the afternoon rain everyday at equator. When strength of northeast wind greater, dry season produced and vice versa.

At equator the sunlight is intense and so water at equator gets heat and temperature of water rises. This results warm water at equator. The intense Sun and warm water heats the air by supplying the excess energy to air in the intertropical convergence zone. This rises the humidity of air and makes it buoyant. With the trade winds , this buoyant air rises. As air ride it expands and cools down in form of droplets. As ITGZ is continuously heated , so every afternoon there is rain. The trade winds and the maximum heating causes the rain in afternoon at equator and wet and dry season instead of summer and winter.