How Do Trade Winds Shape Earth’s Climate Patterns?
Trade winds are a persistent wind that can be defined as the wind that flows towards the equator from the north-east in the northern hemisphere or from the south-east in the southern hemisphere. These are also known as tropical easterlies and are known for their consistency in force and direction.
It is stronger and more consistent over the oceans than over land and often produces partly cloudy sky conditions, characterized by shallow cumulus clouds, or clear skies that make trade-wind islands popular tourist resorts. To understand trade winds it is important to understand what wind is. The wind is defined as the flow of gases or air on a large scale from the high-pressure area to low pressure area.
Classification of Wind
Planetary Winds: Winds that are caused due to air pressure difference from one latitude to another latitude, these winds are also called prevailing winds.
Trade Winds: Winds that blow as south-eastern trades in the Southern hemisphere and as north-eastern trades in the Northern hemisphere. And are primarily caused due to the Coriolis effect and Ferrel’s law.
The Westerlies: The winds that blow from the west towards the east in the middle latitudes between 30° and 60° latitude in both northern and southern hemispheres. These winds get their name from their direction of origin. These are blown from the horse latitudes towards the poles. In the northern hemisphere, these are predominantly from the southwest and in the southern hemisphere, they are from the northwest.
Easterlies: The easterlies or polar easterlies are located between 60° and 90° latitude in both northern and southern hemispheres and are named after the direction they originate from. These are formed when the cool air from the poles sinks and moves towards the equator. These winds are important for sailors as with the help of trade winds only Christopher Columbus discovered America.
Periodic Winds: Winds that change their direction accordingly and are very much dependent on different seasons, like monsoons.
Local Winds: Winds that are caused due to differences in temperature and pressure locally can be classified into conventional, hot, cold, and slope.
What is the Coriolis Effect?
The inertial or fictitious force which is responsible for the deflection of winds to the right in the northern hemisphere and to the left in the southern hemisphere, this phenomenon is known as the Coriolis Effect.
Coriolis effect is used for deriving Ferrel’s law. The Coriolis effect is defined as how a moving object seems to veer toward the right in the Northern hemisphere and left in the Southern hemisphere. The turning of Hurricane winds towards the left in the Northern hemisphere is an example of the Coriolis effect.
There is no Coriolis effect underneath a horizontally and freely moving object at the equator as there is no rotation of the surface of the Earth (sense of turning), and there is no curving of the path for the object as we measure relative to Earth's surface and the object's path is straight, thus causing no Coriolis effect.
Let us have a look at the mathematical representation of the Coriolis Effect using Ferrel’s Law.
The equation of motion in an inertial reference for an object:
F = ma
Where, F= vector sum of all the physical forces acting upon the object, m= mass of the object, a= acceleration of the object which is relative to the inertial reference frame
In order to turn the above equation into a non-inertial reference frame-
\[F-m\frac{d\Omega }{dt}\times r-2m\Omega \times v-m\Omega \times (\Omega \times r)=ma\]
where \[\Omega \] = rotational vector, v= velocity relative to rotating reference frame, r = position vector of object, a= acceleration relative to rotating reference frame
Did You Know?
In northern India, the average maximum temperature is above 33°C in May. It is because of such a high temperature the air of that region heats up and the hot air rises causing a low-pressure area under it, also known as the monsoonal trough. On the contrary, the temperature over the Indian Ocean is relatively low therefore a relatively high-pressure region is created over the sea.
The air from the high-pressure region moves towards the low-pressure region because of the pressure difference between the Indian Ocean and North Central Indian Plains. This signifies that the movement of air is from the equatorial region of the Indian Ocean to the Indian subcontinent in the South-West to North-East direction in June which is exactly opposite to that of the trade winds (North-East to South-West) in India prevailing during winter. The reversal in direction of the wind from North-East to South West and vice-versa is called monsoons. These winds are heavily moisture-laden and cause widespread rain throughout India and from June to September when they move over the Indian subcontinent.
Conclusion
This is all about different types of winds and the elaborate explanation of trade winds. Learn how these winds are formed and what factors influence their flow.
FAQs on Trade Winds: Meaning, Causes & Importance
1. What are trade winds and where are they found?
Trade winds are very steady winds that blow from east to west just north and south of the equator. They are considered a type of planetary wind because they are a permanent and large-scale feature of the Earth's atmosphere. You can find them in a belt that circles the globe, generally between 30° north and 30° south latitude.
2. What is the main cause of the trade winds?
The primary cause of trade winds is the sun's energy. At the equator, intense sunlight heats the air, causing it to become lighter and rise, creating a zone of low pressure. To fill this gap, cooler, denser air from higher latitudes (around 30° North and South) flows towards the equator. This continuous movement of air is what forms the trade winds.
3. Why do the trade winds blow from east to west and not straight down to the equator?
Trade winds blow from east to west because of the Earth's rotation. This rotation creates a phenomenon known as the Coriolis effect, which deflects moving objects (like air) to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. So, instead of flowing directly south or north towards the equator, the winds are curved, resulting in their consistent easterly direction.
4. What is the historical reason they are called 'trade winds'?
The name 'trade wind' comes from their importance to early sailors and commerce. For centuries, the captains of sailing ships depended on these highly predictable and reliable winds for crossing the world's oceans. The term 'trade' historically meant 'path' or 'track,' so these winds provided a dependable track for ships engaged in trade.
5. How are trade winds different from the westerlies?
The key differences between trade winds and westerlies are their location and direction of flow. Here’s a simple breakdown:
- Location: Trade winds are found in the tropics, between the equator and 30° latitude. Westerlies are located in the mid-latitudes, between 30° and 60°.
- Direction: Trade winds blow from the east towards the west. Westerlies, as their name suggests, blow from the west towards the east.
- Air Flow: Trade winds flow towards the low-pressure equatorial belt, while westerlies flow away from the subtropical high-pressure belts towards the poles.
6. What happens to global weather when the trade winds weaken?
When trade winds weaken, it can significantly disrupt global weather patterns. A classic example is the El Niño phenomenon in the Pacific Ocean. During El Niño, the Pacific trade winds weaken or even reverse, which changes ocean surface temperatures. This can lead to severe weather events like droughts in places like Australia and Indonesia, and heavy rains or floods in parts of North and South America.
7. How does the Coriolis effect influence trade winds in both hemispheres?
The Coriolis effect acts differently in each hemisphere, but the result is a westerly flow for both sets of trade winds. In the Northern Hemisphere, air moving south towards the equator is deflected to its right, creating the northeast trade winds. In the Southern Hemisphere, air moving north towards the equator is deflected to its left, creating the southeast trade winds.
8. What are some of the main characteristics of trade winds?
Trade winds have several distinct characteristics:
- They are known for their consistency in both speed and direction.
- As they are warm winds blowing over vast oceans, they pick up a great deal of moisture.
- They are responsible for bringing heavy rainfall to the eastern sides of continents in tropical areas.
- The area near the equator where the northeast and southeast trade winds meet is called the Intertropical Convergence Zone (ITCZ), often known for its calm winds called the doldrums.
9. If the Earth stopped rotating, how would wind patterns be different?
If the Earth did not rotate, the Coriolis effect would not exist. In this scenario, wind would flow in a very simple, direct path from high-pressure areas to low-pressure areas. Air from the subtropics (30° N/S) would blow straight to the equator. This would create a simple north-to-south wind in the Northern Hemisphere and a south-to-north wind in the Southern Hemisphere, and the familiar east-to-west trade winds would disappear completely.
