Types of Wind

In climatology, wind is the movement of air relative to the Earth’s surface. Winds are important in determining and managing the environment and weather.

Wind is caused by horizontal and vertical pressure variations (gradients) in the atmosphere. As a result, wind distribution is closely related to pressure distribution. Winds near the Earth’s surface usually flow around cyclones and anticyclones, which are areas of relatively low and high pressure, respectively. They rotate clockwise around Northern Hemisphere lows and anti-clockwise around Southern Hemisphere lows. Similarly, wind systems revolve in the opposite direction around the centres of highs.

Types of Wind

Winds are broadly categorised into three types:

• Permanent or Planetary Winds

These are the large-scale planetary winds that sweep across continents and oceans. The two most well-known and vital winds for climate and human activities are trade winds and westerly winds.

• Trade Winds: Winds blowing from subtropical high-pressure areas to the equatorial low-pressure belt are known as trade winds. As a result, they are only found between 30°N and 30°S on the earth’s surface. In the northern hemisphere, they flow as north-eastern trades, while in the southern hemisphere, they flow as south-eastern trades. These winds are known as trade winds because their direction (of trade winds) is more or less constant and regular, which benefited sea merchants in sailing their ships.
• Westerlies:The westerlies are winds that move from subtropical high-pressure belts (30°-35°) to sub-polar low-pressure belts (60°-65°) in both hemispheres. In the northern hemisphere, they blow from the south-west to the north-east, while in the southern hemisphere, they blow from the north-west to the south-east. The westerlies are stronger and more persistent in the southern hemisphere due to the immense expanse of ocean, but they are irregular in the northern hemisphere due to the uneven relief of vast land masses.
• Polar easterlies: In the Northern Hemisphere, polar easterlies blow from the north-east to the south-west, while in the Southern Hemisphere, they blow from the south-east to the north-west. They come from the subpolar lows’ polar high-pressure zones.

• Secondary Winds or Periodic Winds

As the seasons change, the direction of these breezes shifts. The best example of large-scale wind system change on a global scale is monsoons. Periodic winds include land and sea breezes, mountain and valley breezes, cyclones and anticyclones, and air masses.

• Monsoons: Once upon a time, monsoons were supposed to be a large-scale combination of land and sea breezes. As a result, they were dubbed “massive convectional circulation.” A seasonal shift in wind direction distinguishes the monsoons.

During the summer, the southern hemisphere’s trade winds are dragged northwards by an apparent northward shift of the sun, as well as a powerful low-pressure centre in the north-west of the Indian subcontinent. When these winds cross the equator, they are deflected to the right due to Coriolis force.

• Land Breeze and Sea Breeze: Land and sea absorb and transfer heat in different ways. The ground heats up faster than the sea throughout the day, becoming warmer than it is at night. As a result, the air rises over the land, resulting in a low-pressure area, whereas the sea is cooler and the pressure overseas is relatively high. As a result, the sea breeze blows from the sea to the land, creating a pressure gradient between the ocean and the land. During the night, a condition reversal happens. The land loses heat more quickly than the water, so it is cooler. A land wind is caused by a pressure differential from land to sea.
• Valley Breeze and Mountain Breeze: The slopes in hilly places heat up during the day, causing air to flow upslope, and air from the valley blows up the valley to fill the resulting gap. This wind is referred to as the valley breeze. During the night, the mountain breeze cools the slopes, and dense air descends into the valley. The frigid air from the high plateaus and glacier fields that drain into the valley is known as the katabatic wind.

• Tertiary Winds or Local Winds

Local winds are caused by changes in temperature and pressure. Such winds have a localised influence and are limited to the lowest areas of the troposphere. Some examples of local winds are listed below.

• Loo: The loo has the potential to be harmful. A very hot and dry wind blows from the west through the plains of northern India and Pakistan in the months of May and June, usually in the afternoons. It is known as It has a constant temperature of 45 to 50 degrees Celsius. People may experience sunstroke as a result of it.
• Foehn or Fohn: This is a good wind. In the Alps, Foehn is a heated breeze of local significance. On the leeward side of a mountain range, a strong, gusty, dry, and warm wind blows. The air that falls on the leeward side is dry and hot because the windward side takes away any moisture in the entering wind in the form of orographic precipitation (Katabatic Wind). 

The wind ranges in temperature between 15 and 20 degrees Celsius. By melting snow, the wind speeds up the ripening of grapes and makes it simpler for animals to graze.

• Chinook: This is a good wind. In the United States and Canada, Foehn-like winds blow down the west slopes of the Rockies. It benefits ranchers east of the Rockies because it keeps the grasslands free of snow for the majority of the winter.
• Mistral: Wind Has the Potential to Be Harmful. The Mistral is a wind that blows from the Alps over France and into the Mediterranean Sea. The Rhine River runs through the Rhine Valley. It’s bitterly cold and dry, with a brisk breeze. Blizzards are widespread in southern France as a result of this.
• Sirocco:This wind has the potential to be harmful. Sirocco is a Mediterranean wind that sweeps at hurricane-force speeds across North Africa and Southern Europe. It originates in the Sahara. Low-pressure systems migrating eastward across the Mediterranean Sea draw a warm, dry tropical air mass northward, with wind from the Arabian or Sahara deserts. The maritime cyclone’s cooler, wetter air combines with the continent’s hotter, drier air, and the low’s anti-clockwise circulation propels the mixed air across Europe’s southern shores.

The Sirocco provides dusty, dry weather to northern Africa, storms to the Mediterranean Sea, and cold, rainy weather to Europe.

Conclusion

The natural movement of air or other gases relative to a planet’s surface is referred to as wind. Winds occur on a variety of scales, from tens of minutes thunderstorm flows to local breezes generated by land surface heating that last a few hours to global winds caused by differences in solar energy absorption between climate zones on Earth. The differential heating between the equator and the poles, as well as the planet’s rotation, are the two fundamental drivers of large-scale atmospheric circulation (Coriolis effect). Thermal low circulations over topography and high plateaus can cause monsoon circulations in the tropics and subtropics.

Local winds in coastal locations can be defined by the sea breeze/land breeze cycle; in areas with diverse terrain, mountain and valley breezes can prevail.