Earth’s Systems


What is Wind?

Ever wonder why the wind blows? Wind is just air moving around. It moves from places where there’s a lot of it (high pressure) to places where there isn’t much (low pressure). And guess what makes it move? Temperature! When air heats up, it rises, leaving less air (or low pressure) below. Cooler air then rushes in to fill that space, and voila! That’s wind.

Winds that Travel the World

Some winds are big travelers; they blow steadily over long distances from specific directions. These are called global winds, and they’re caused by the sun heating up the Earth unevenly. Here are some of the main global winds:

  • Trade Winds: These winds blow from east to west near the equator. They’re steady and reliable, which made them really helpful for sailing ships long ago. That’s why they’re called ‘trade winds’.
  • Westerlies: These winds are found in the middle latitudes, and they blow from west to east. If you live in North America or Europe, these are the winds that often bring your weather.
  • Polar Easterlies: These winds blow from east to west, away from the poles. They’re usually cold and dry.

Winds Close to Home

Then there are local winds. These are like neighborhood winds that don’t go very far. They’re influenced by things like mountains, valleys, and bodies of water, and can change direction and speed throughout the day. Here are a few examples:

  • Sea Breezes and Land Breezes: During the day, land gets hotter faster than the sea. The air above the land rises, and the cooler air over the sea rushes in to replace it, creating a ‘sea breeze’. At night, the process flips, creating a ‘land breeze’.
  • Mountain and Valley Breezes: Just like sea and land breezes, these are caused by temperature differences. During the day, air rises up mountainsides, creating a ‘mountain breeze’. At night, the air cools and falls into valleys, creating a ‘valley breeze’.
  • Chinook Winds: These are warm, dry winds that blow down the east side of the Rocky Mountains. They can make temperatures rise super fast, often melting snow and ice.

The Wind’s Big Job

Winds have an important job to do. They move heat and moisture around the Earth, which affects our weather and climate. For example, westerly winds often carry moist air from the ocean over the land, causing rain. On the other hand, chinook winds can create dry conditions and quick warm-ups.