Determining Stability » Potential Instability Lifted Example

To apply this concept of potential instability to vertical displacement of the layer, let's examine the same initially stable layer as the previous example. First lift the layer by 100 hPa, and then examine the resulting lapse rate. The lifted layer becomes conditionally unstable because the lift causes the bottom of the layer, where there is greater moisture content, to saturate and cool at the moist (saturation) adiabatic lapse rate while the drier top of the layer cools at the dry adiabatic rate—the result: the layer's lapse rate steepens. Thus, the unlifted layer is potentially unstable.