The HUGE clouds





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The cumulonimbus and the nimbostratus


We discussed the nimbostratus clouds in one of the previous lessons (the Darkest Layer).

However, one of the very dramatic clouds is the cumulonimbus cloud or the "heaps of rain" cloud. 

This cloud has a lot of dark colors in the lower part of the cloud.

The top 2/3  of the cumulonimbus cloud has very densely packed heaps of white cumulus clouds. 

It is as if a giant standing on the earth was inserting an air pump into the bottom of the cloud. 

And inflating the cloud with air. 

The cumulonimbus cloud is a super-sized cumulus and nimbostratus clouds put together, spanning from the lower levels of the Troposphere to its highest levels. 

It is the cumulonimbus cloud that is responsible for severe weather such as thunderstorms, torrential rain, hailstorms, and tornadoes.

Why do we have hail?

Does seeing clouds as different combinations of freezing and amounts of liquid water droplets help you see how hail forms?

Take a cumulus cloud with a large amount of microscopic liquid water droplets and lots of air. Suppose a cold updraft pushes up into the cloud.

The pressure from the updraft forces a large amount of the liquid droplets upwards as well as air. The liquid droplets freeze against each other in the much colder higher altitudes.

The high pressure from the cold wind pushes each frozen ice bundle together, compacting and enlarging them as they bounce around in the cold up-reaches of the cloud.

When those compact ice bundles get heavy enough, they fall as hail. 

White hail. 


The huge clouds have a lot of everything: 

water vapor, air, and liquid water droplets. 

Cumulonimbus clouds, in particular,

have lots of air updrafts. 

It is as if a giant were standing on earth and

pumping air into the cloud

with an air pump.

Picture Credits:

  1. Pattys-photos . clouds. Flickr photo-sharing. Taken Aug 9, 2011.
  2. Bernard DUPONT. Cumulonimbus Cloud Somewhere above MALAYSIA. Flickr photo-sharing. Taken on Nov 14, 2015.

The HUGE clouds


About the teacher

Juman Hijab

Juman is a retired physician after having been in clinical practice for more than four decades. Her lifelong interest has been in the chemistry of life.