Study Notes on Types of Winds (Part-1)

TYPES OF WINDS

I. Planetary winds:

Planetary winds are major component of the general global circulation of air. These are known as planetary winds because of their prevalence in the global scale throughout the year. Planetary winds occur due to temperature and pressure variance throughout the world.

The planetary winds are discussed below:

(a) Trade wind

Winds blowing from the Subtropical High Pressure Belt or horse latitudes towards the Equatorial Low Pressure Belt or the ITCZ are the trade winds. In the Northern Hemisphere, the trade winds blow from the northeast and are known as the Northeast Trade Winds; in the Southern Hemisphere, the winds blow from the southeast and are called the Southeast Trade Winds. The weather conditions throughout the tropical zone remain more or less uniform. This belt is subjected to seasonal variation due to northward and southward movement of sun. The equatorward part of the trade wind are humid because they are characterized by atmospheric instability thus causes heavy precipitation.

(b) Westerly Wind

The Westerlies are the prevailing winds in the middle latitudes between 35º and 65º latitude, blowing from the high pressure area in the Sub Tropical High Pressure Belt i.e. horse latitudes towards the sub polar low pressure belt. The winds are predominantly from the south-west to north-east in the Northern Hemisphere and from the north-west to south-east in the Southern Hemisphere. The Westerlies are strongest in the winter season and times when the pressure is lower over the poles, while they are weakest in the summer season and when pressures are higher over the poles. The Westerlies are particularly strong, especially in the Southern Hemisphere, as there is less land in the middle latitudes to obstruct the flow. The Westerlies play an important role in carrying the warm, equatorial waters and winds to the western coasts of continents, especially in the Southern Hemisphere because of its vast oceanic expanse.

(c) Polar Wind

The winds blowing in the Arctic and the Antarctic latitudes are known as the Polar Winds. They have been termed the 'Polar Easterlies', as they blow from the Polar High Pressure belt towards the Sub-Polar Low-Pressure Belts. In the Northern Hemisphere, they blow in general from the north-east, and are called the North-East Polar Winds and in the Southern Hemisphere, they blow from the south-east and are called the South- East Polar Winds. As these winds blow from the ice-capped landmass, they are extremely cold. They are more regular in the Southern Hemisphere than in the Northern Hemisphere.