What sign could indicate the presence of a valley breeze?

What sign could indicate the presence of a valley breeze?

• A. Humidity increases
• B. Temperature drops
• C. Speed of the airflow increases
• D. Clouds form

Answer: (C)

A valley breeze is a daytime, thermally driven upslope wind in mountainous terrain. When the sun heats the slopes, air along those slopes rises and draws air from the valley floor up toward the slopes. This creates a noticeable increase in wind speed in the valley as the air moves upslope to replace what has risen. So the most reliable sign is the speed of the airflow increasing. Humidity changes or clouds aren’t definitive indicators of a valley breeze, and a simple temperature change isn’t as directly tied to the presence of this local wind as the observable upslope, increasing wind.

A valley breeze is a daytime, thermally driven upslope wind in mountainous terrain. When the sun heats the slopes, air along those slopes rises and draws air from the valley floor up toward the slopes. This creates a noticeable increase in wind speed in the valley as the air moves upslope to replace what has risen. So the most reliable sign is the speed of the airflow increasing. Humidity changes or clouds aren’t definitive indicators of a valley breeze, and a simple temperature change isn’t as directly tied to the presence of this local wind as the observable upslope, increasing wind.