Source region facts for kids

A Source Region in meteorology is a special area where large bodies of air, called air masses, pick up their unique traits. These traits include how warm or cold they are (their temperature) and how much water vapor they hold (their humidity). Think of it as a "home base" for an air mass, where it gets its personality before moving around the world.

A source region can be either a large area of land or a big body of water. If an air mass forms over water, like an ocean, it's called a maritime air mass. If it forms over land, it's known as a continental air mass. The type of surface below the air mass makes a big difference in what kind of weather it will bring.

What Makes a Source Region Special?

A source region needs to be a large, flat area where the air can stay still for a while. This allows the air to take on the temperature and moisture of the surface below it. For example, if air sits over a hot, dry desert for several days, it will become hot and dry itself. If it stays over a warm ocean, it will become warm and moist.

These regions are important because they are where air masses get their starting characteristics. When these air masses move, they carry their "personality" with them, influencing the weather in new places.

Types of Source Regions

Source regions are usually grouped into two main types: continental (land-based) and maritime (water-based). Each type gives the air mass different qualities.

Land-Based Air Masses

When an air mass forms over a large area of land, it becomes a continental air mass. These air masses are typically dry because there isn't much water to evaporate into the air. Their temperature depends on whether the land is hot or cold.

• Continental Polar (cP): These form over cold, snow-covered land areas, like northern Canada or Siberia. They bring very cold, dry weather.
• Continental Arctic (cA): Even colder and drier than cP, these form over the Arctic regions. They bring extremely cold, crisp air.
• Continental Tropical (cT): These form over hot, dry deserts, like the Sahara or the southwestern U.S. They bring hot, dry weather.

Ocean-Based Air Masses

Air masses that form over oceans or large bodies of water are called maritime air masses. They are always moist because water evaporates from the surface into the air. Their temperature depends on whether the water is warm or cold.

• Maritime Polar (mP): These form over cold ocean areas, like the North Atlantic or North Pacific. They bring cool, moist weather, often with clouds and rain.
• Maritime Tropical (mT): These form over warm ocean areas, like the Gulf of Mexico or the Caribbean Sea. They bring warm, humid weather, often leading to thunderstorms and heavy rain.

How Source Regions Affect Our Weather

The characteristics an air mass picks up in its source region are what determine the weather it brings to other places. For example:

• A cold, dry continental polar air mass moving into a warmer area can cause temperatures to drop sharply.
• A warm, moist maritime tropical air mass can bring humid conditions, clouds, and rain or thunderstorms.

Understanding source regions helps meteorologists predict what kind of weather is coming our way. By knowing where an air mass originated, they can better forecast temperatures, humidity, and precipitation.