Figure 2-22 Stable, Unstable, and Neutral Stability
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
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