Question

Westerlies blow from the South West in _______________.
A.Northern Hemisphere
B.Southern Hemisphere
C.Eastern Hemisphere
D.Western Hemisphere

Answer 1

Hint: The wind system over the earth’s surface is determined by various factors that affect them like latitudes, temperature, pressure, angle of sun rays, etc. The prevailing winds are the surface winds that blow predominantly over a given region from a particular direction. There are three main prevailing winds— the trade winds, the westerlies and the polar easterlies.

Complete answer:
1)The trade winds blow in the equatorial region between the latitudes 30°N and 30°S;

2)The westerlies that blow in the mid-latitudes between 30°-60° in both hemispheres (most commonly referred to as roaring forties, furious fifties and shrieking sixties); and

3)The polar easterlies that blow in the polar region between 60°-90° in both hemispheres.

Option A: is correct. The Westerlies blow from the south-west in the Northern Hemisphere. The westerlies are the strongest in the roaring 40s i.e the latitudes between 40-50°. The westerlies result from the Coriolis effect caused by the earth’s rotation which tends to deflect poleward winds eastward from the north in the Northern Hemisphere and eastward from the south in the Southern Hemisphere.

Option B: is incorrect. The Westerlies blow from the north-west in the Southern Hemisphere. The Westerlies are stronger in the Southern Hemisphere especially in areas where land is absent because land amplifies the flow pattern and slows the westerlies.

Options C and D: are incorrect. This is because the eastern and western hemisphere as indicated by longitudes attribute to the rotation of the earth that results in day and night and subsequent time zones. A difference of 15° longitude corresponds to a one-hour difference in local time. Therefore, the eastern and western hemispheres do not necessarily affect the wind and pressure system of earth.

Hence, the correct answer is option (A)

Note: The westerlies give rise to extratropical cyclones in the mid-latitudes which can develop into a subtropical cyclone and then to a tropical cyclone if it blows over warm waters and develops central convection.