What happens to the characteristics of an air mass as it moves over other areas?

As an air mass moves over different areas, its characteristics can change based on the underlying surface. This process is known as air mass modification. Here are the steps that describe what happens:

1. Origin: An air mass originates over a particular region. The characteristics of this air mass (temperature, humidity, etc.) are determined by the underlying surface of this region. For example, an air mass forming over a desert will be hot and dry.

2. Movement: The air mass starts to move, driven by the larger atmospheric circulation patterns. It can move over land or water, and over different types of terrain (mountains, plains, etc.).

3. Interaction with the Surface: As the air mass moves over a new area, it starts to interact with the surface of that area. If the air mass moves over a body of water, it can pick up moisture, becoming more humid. If it moves over a colder region, it can cool down.

4. Modification: These interactions with the new surface can modify the characteristics of the air mass. A hot and dry air mass can become cooler and more humid after moving over a body of water. Similarly, a cold and humid air mass can become warmer and drier after moving over a hot desert.

5. Impact: These changes in the air mass can affect the weather in the areas it moves over. For example, a modified air mass can bring rain, snow, or changes in temperature.

So, the characteristics of an air mass are not fixed, but can change as the air mass moves and interacts with different surfaces.