In which directions do you normally expect winds to blow in the two latitude belts of 0 degree to 30 degrees North and 0 degree to 30 degree South ? Give reasons....
Answers
Answer: The winds in the latitude belt 0 to 30 degrees South are expected to blow in the the northwest direction. This is due to the prevailing Southeasterly Trade winds [1].
Similarly, the most frequent winds in the latitude belt 0 to 30 degrees North are in the southwest direction, however with some geographical limitations. While the Northeasterly Trade Winds are prevalent in the region of Pacific ocean, South America, Saharan and Sub-Saharan Africa, the situation is different in South and South-East Asia, where the prevailing wind changes between southwestern and northeastern direction.
The main reason for the prevailing wind in tropics is the Hadley cell [2] driven by the heating of the air by the surface and the Earth’s rotation. The Earth’s surface is generally warmest around the equator. The warm air there is rising up to the upper troposphere, where it starts moving towards poles. As the air cools, it encounters stronger horizontal winds at the latitude 30 deg, and descends towards the surface.
Once the air is by the surface, it starts warming up and is pushed by the differences in the density towards the equator. As the earth rotates and lower latitudes have higher circumference, the air moving towards the equator is slower relative to the surface of the Earth, and therefore the wind starts turning towards west.
This is indeed a simplified explanation, and the zone where the hedley cells are located shifts south and north twice during the year. Furthermore, there are number of regional and coastal phenomena that also change wind direction.