FAA Aircraft Dispatcher Practice Exam

What is a dry line and its characteristic effect?

1. A boundary separating two cold air masses

2. A boundary that separates a moist air mass from a dry air mass

3. A line depicting hot and humid weather

4. A front created by sea breezes

The correct answer is: A boundary that separates a moist air mass from a dry air mass

A dry line refers to a boundary that separates a moist air mass from a drier air mass. This phenomenon is significant in meteorology, particularly in the formation of severe weather such as thunderstorms. The characteristic effect of a dry line is that it often serves as a trigger for convection. When moist air, often originating from bodies of water, moves towards a dry line, it can lead to the uplifting of the moist air as it encounters the denser, dry air. This can create instability in the atmosphere, conducive to thunderstorm development and, in some cases, severe weather events. The presence of the dry line can markedly influence local weather patterns, particularly in areas like the Great Plains of the United States, where the clash of these different air masses is common. Understanding this phenomenon is essential for forecasting severe weather and planning for aviation operations.