What does the term "jet stream" refer to in meteorology?

The term "jet stream" in meteorology specifically refers to a fast-flowing ribbon of air located high in the atmosphere, typically found at altitudes of around 30,000 to 40,000 feet. These streams are significant because they influence weather patterns by affecting the movement of air masses and the formation of storms. Jet streams are characterized by their high speeds, often exceeding 100 miles per hour, and their direction usually flows from west to east, although they can meander and shift.

Understanding the jet stream is crucial for forecasting changes in weather, as they act as a barrier and guide for various systems in the atmosphere. For instance, the position and intensity of the jet stream can determine where weather fronts develop and how they move, which is fundamental in predicting conditions such as rain, snow, and temperature fluctuations.

The other options present definitions that do not accurately characterize the jet stream. A slow-moving air mass near the surface does not align with the high altitude and speed of the jet stream. A layer of clouds in the lower atmosphere does not reflect the concept of jet streams, which deal with high-altitude winds rather than cloud formations. Additionally, jet streams are not a seasonal phenomenon; they can occur year-round but may exhibit variations in