3. Stability

Changing Stability » Vertical Motion Divergence in the Lower Atmosphere

Now let's look at the effects of divergence and convergence on stability. In order to simplify the discussion, we will assume that the elevation of the layer remains constant while divergence or convergence occurs. We can make this assumption for the special case of a surface-based layer.

First, let's look at the case of divergence. With divergence, we horizontally stretch an air mass, so its area increases. In response, the surface-based layer thins. As the top of the layer descends, it warms at the dry adiabatic lapse rate. This change acts to stabilize the layer.