Dear Tom,
Why is it that clouds are flat at the bottom and have irregular shapes on top?
Hans Weckerle
Dear Hans,
You have described cumulus clouds, the "dab of cotton" clouds that populate the sky on warm afternoons. When warm air ascends in rising currents, its pressure falls and its temperature drops at a steady rate of 5.4 degrees per 1,000 feet of vertical climb.
Rising air, if the process continues long enough, eventually ascends to a critical height and chills to a critical temperature at which its load of water vapor suddenly begins to condense. That defines the flat bottom of a cumulus cloud.
However, ongoing condensation at the cloud top, rather than being limited by specific air pressure and temperature values, occurs in irregular surges determined by constantly varying factors like available moisture and updraft strength.
Why is it that clouds are flat at the bottom and have irregular shapes on top?
Hans Weckerle
Dear Hans,
You have described cumulus clouds, the "dab of cotton" clouds that populate the sky on warm afternoons. When warm air ascends in rising currents, its pressure falls and its temperature drops at a steady rate of 5.4 degrees per 1,000 feet of vertical climb.
Rising air, if the process continues long enough, eventually ascends to a critical height and chills to a critical temperature at which its load of water vapor suddenly begins to condense. That defines the flat bottom of a cumulus cloud.
However, ongoing condensation at the cloud top, rather than being limited by specific air pressure and temperature values, occurs in irregular surges determined by constantly varying factors like available moisture and updraft strength.
