3. Stability

Determining Stability » Potential Instability Introduction

Photo of stratocumulus clouds

The stability criteria for small parcel displacements, while generally applicable and widely used, are not indicative of what might happen when layers or parcels are given larger vertical displacements. Such displacements would cause whole layers to change their type of stability over a broad area, or would cause parcels to cool adiabatically to saturation and to perhaps penetrate deeply into layers having different stability.

As a result, a number of procedures have been proposed to apply the parcel theory to this problem of large vertical displacements. One such approach to the lifting problem involves the concept of potential instability, in which the effect of bodily lifting any layer is considered.