Winds

Local and Global Winds

By: Alex Freeman

General Information

Definition:

Wind is the horizontal movement of an area of high pressure to an area of lower pressure.


What Causes Wind?

Winds are caused by differences in air pressure.

Local Winds

Definition:

Local winds are winds that blow over a short distance.


How They Are Created:

Local winds are caused by the unequal heating of Earth's surface.

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Local Winds: Sea Breeze

What It Is:

Movement of air from the sea to the land.


When It Occurs:

Sea Breezes occur during the day.


Convection Current Steps:
  • Air over water is cooler than air over land due to the land being warmer than the water.
  • The cool air is higher in pressure and moves under warm air.
  • The warm air expands and rises because it's less dense and has a lower air pressure.
  • The denser, cool air then sinks causing the air to blow towards the shore.

Local Winds: Land Breeze

What It Is:

Movement of air from land to sea.


When It Occurs:

Land Breezes occur in the evening.


Convection Current Steps:

  • Air over land becomes cooler than the air over the water due to land cooling faster than water.
  • The cooler air is more dense so it's at a higher pressure thus making it sink over the land and move beneath the warmer air.
  • Warm air over the water is at a lower pressure due to it expanding. It then rises.
  • The warm air is then cooled and becomes more dense from the colder temperatures in the atmosphere.
  • The cool dense air is now at a high pressure and sinks over the land.

Global Winds

What They Are:

A wind that blows steadily over long distances typically blowing at the same speed and from the same direction.


Besides the fact that they occur because of the unequal heating of Earth's surface, global winds are mainly a giant convection current between the equator and the poles. In the northern hemisphere, winds turn to the right closer to the equator whereas in the southern hemisphere, winds turn towards the left.

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Global Winds: Horse Latitudes

What They Are:

Horse Latitudes are calm areas of sinking air. They are very weak.


Where They Occur:

Horse Latitudes can be found at 30 degrees north and south latitude.


Fun Fact:

Horse Latitudes got their name from people on long voyages running out of food and water so out of the animals they had, they would throw dead and alive horses overboard into the sea.

Global Winds: Trade Winds

What They Are:

These winds are very strong and blow from the horse latitudes towards the equator.


Where They Occur:

Trade Winds lie between 0 degrees and 30 degrees latitude.


What They Are Used For:

Sailors use them to help sail across the ocean with cargo to trade things. That's also how they got their name.

Global Winds: Jet Streams

What They Are:

A band of very strong powerful winds that flows west to east.


Where They Occur:

Jet Streams are found in the upper troposphere.


What They Are Used For:

Airplanes and jets use jet streams if they are going east to travel faster and save fuel.

Global Winds: Prevailing Westerlies

What They Are:

Polar Westerlies are winds that blow away from the horse latitudes. This means they blow from the west.


Where They Occur:

These winds can be found between 30 degrees and 60 degrees latitude in the northern hemisphere. Polar easterlies are the same thing but occur in the southern hemisphere.