Methods Of Lifting

CHAPTER TWO

AVIATION WEATHER

Figure 2-22 Stable, Unstable, and Neutral Stability

210.

METHODS OF LIFTING

The four methods of lifting are convergence, frontal, orographic, and thermal (Figure 2-23).

Convergence of two air masses, or parts of a single air mass, force the air upward because it has

nowhere else to go. Because of the shape of cold fronts, as they move through an area, they will

lift the air ahead of the cold air mass. Orographic lifting is a term indicating the force of the

wind against a mountainside pushes the air upward. Thermal lifting, also known as convective

lifting, is caused when cool air is over a warm surface and it is heightened by intense solar

heating on a clear day.

Figure 2-23 The Four Lifting Methods

211.

STABILITY AND FLIGHT CONDITIONS

Cloud types are helpful in identifying conditions of stability or instability. Cumuliform clouds

develop with unstable conditions and stratiform clouds develop with stable conditions

(Figure 2-24), assuming sufficient moisture exists for cloud development.

2-22 Atmospheric Mechanics of Winds, Clouds and Moisture, and Atmospheric Stability