Lifting by Convergence
broad lifting of an entire layer of air
When the horizontal flow of air
converges along the
earth's surface, it must go somewhere. Since it is not able to go into the
ground, it rises.
Large scale convergence
lifts a layer
of air (sometimes hundreds of kilometers across),
the air cooling as it rises.
If the rising air cools to its saturation point,
the water vapor will condense out to form cloud droplets.
Vertical motions associated with convergence lifting
are typically much weaker than the stronger small scale vertical
motions associated with
convective processes. As a result,
clouds generated through convergence are less vertically developed.
Cirrostratus clouds is one cloud type
that develops from convergence lifting.
It is also important to note
that convergence occurs not only at the surface, but
higher levels as well.