Nimbostratus clouds
Why does it rain?
Our typical rain clouds: the nimbostratus clouds
The image above shows the dark clouds that make up the nimbostratus clouds.
The nimbostratus clouds produce a leaden grey sky. They result in continuous rain over several hours.
Why does rain fall from the cloud? Why does it fall in rain drop fashion rather than larger amounts if the "sky is opening up"? In this article, I will use the analogy of a wet sponge to explain rain clouds
Altostratus clouds
Rain clouds start with an altostratus cloud
First: Use a cloud that is extensive and filling the sky
What is really interesting is that as you add more water vapor to a cloud, it gets heavier and more grey. Thus, a white cirrostratus descends in the sky to become a grey altostratus. And a grey altostratus descends in the sky to become a dark gray/black nimbostratus.
Nimbostratus - altostratus
Rain clouds increase their water content by several fold
Second: Add a warm front that has a lot of warm water vapor
Have you noticed that as soon as the rain stops that the clouds no longer have that darkened structure?
Nimbostratus clouds with rain
Rain Clouds with lots of water are heavier
Third: The heavy water-laden cloud is squeezed out like a wet sponge
Picture credits:
- Header image: Paulo O. Storm Clouds Over Fairfax, April 27, 2011.
- Nicholas A. Tonelli. Spotlight. Storm clouds, northeast Lehigh Valley, Sept 24, 2006.
- Maxwell Hamilton. Unusual Clouds; Altostratus undulatus, March 30, 2015.
- Nicholas A. Tonelli. Convergence, Nimbostratus streaks, Easton, March 24, 2007.
- Melissa Gutierrez. Nimbostratus clouds. Same clouds as the previous picture, only after getting into them and the accompanying light rain, July 29, 2001.