Ask Brandon: What kind of clouds are these and what makes clouds do this?


What kind of clouds are these and what makes clouds do this?

– Don R, Nashville, TN

Dear Don,

These clouds are called gravity waves, and they are made by, you guessed it, gravity!

Let’s break it down a little more. A gravity wave is a vertical wave of air. These waves move through the air similar to ripples in a pond after a rock or something has splashed in. As the distance from the point where the rock hit the water increases, the waves become weaker. This is also similar to gravity waves.

Now to start a gravity wave something has to set it into motion. The top two causes of these waves are mountains or thunderstorms. Jet stream shear and solar radiation are other sources but we won’t really get into those. The air from a mountain is pushed upward as it rises along the slope, however if the environment is stable (not conducive for thunderstorms) the air is then forced downward towards it’s equilibrium point, but it in this case it sort of acts as a bouncy ball and bounces back and forth up and down.

In a gravity wave, the upward moving region is the most favorable region for cloud development and the sinking region favorable for clear skies. If there is enough moisture that is where you will see clouds form and is why you may see rows of clouds and clear areas in between. This is a sign of some strong turbulence, so while they are fun to look at, hopefully your pilot keeps you away from them!

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