WESTERLIES

Introduction:

The westerlies are the winds blowing from the sub-tropical high pressure belts towards the sub polar low pressure belts.

They blow from south­west to north-east in the northern hemisphere and north-west to south-east in the southern hemisphere.

The westerlies are best developed between 40° and 65°S latitudes. These latitudes are often called Roaring Forties, Furious Fifties, and Shrieking Sixties – dreaded terms for sailors

What exactly are Westerlies?

• The westerlies are mainly the winds moving from subtropical high-pressure belts to subpolar low pressure belts.
• They blow from the southwest to the northeast in the northern hemisphere, and from the northwest to the southeast in the southern hemisphere.
• The westerlies in the southern hemisphere are stronger and more persistent due to the great expanse of the ocean, but those in the northern hemisphere are irregular due to uneven relief of vast landmasses.

How Westerlies Form?:

• Polar Cell Circulation: Westerlies are a component of the Polar Cell, a major atmospheric circulation pattern. At the poles, cold air descends, creating high pressure zones. This air then flows towards the equator, warming and rising around 60° latitude, creating low pressure zones.
• Hadley Cell Circulation: The descending air from the Hadley Cells (near 30° latitude) also contributes to the low pressure zone at 60° latitude.
• Coriolis Effect: As the air moves from high to low pressure zones, it is deflected by the Coriolis effect, a force caused by Earth’s rotation. This deflection causes the wind to blow from west to east in the middle latitudes.

Characteristics of Westerlies:

• Prevailing Direction: Westerlies consistently blow from west to east, hence the name “prevailing westerlies.”
• Variable Strength: The strength of westerlies can vary depending on factors like season, latitude, and local topography.
• Influence on Weather: Westerlies play a significant role in weather patterns, bringing storms and precipitation to the temperate zones.
• Jet Streams: Westerlies are closely associated with jet streams, narrow bands of strong winds located high in the atmosphere. These jet streams act as boundaries between cold polar air and warmer tropical air, influencing the movement of weather systems.

Impact on Global Climate:

• Temperate Climates: Westerlies are the primary winds that influence the climates of temperate zones, bringing moisture and cooler temperatures to these regions.
• Ocean Currents: Westerlies drive major ocean currents, including the Gulf Stream and the Kuroshio Current, which transport warm water from the tropics towards the poles, moderating the climate of coastal regions.
• Plant and Animal Distribution: The climates influenced by westerlies support a wide variety of plant and animal life adapted to temperate conditions.

Historical and Modern Significance:

• Navigation: Sailors have used the westerly winds for centuries to sail across the Atlantic and Pacific oceans, particularly in the southern hemisphere where the winds are stronger and more consistent.
• Weather Forecasting: Understanding the dynamics of westerlies is crucial for weather forecasting, as they play a significant role in the movement of storms and precipitation patterns.
• Climate Change: Climate change is altering global circulation patterns, including the intensity and trajectory of westerlies. This could have significant implications for weather patterns, ocean currents, and climate in temperate zones.

PYQ Consider the following statements: (UPSC-2021) 1. In the tropical zone, the western sections of the oceans are warmer than the eastern sections owing to the influence of trade winds. 2. In the temperate zone, westerlies make the eastern sections of oceans warmer than the western sections. Which of the statements given above is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2