Gravity Waves
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Hello Don, as you already suspected the mentioned gravity waves in the CAD of the 26th of May are not the kind of gravity waves Albert Einstein once predicted to exist and indeed can be caused by a supernova. That’s a very different league so to speak.
In next link you will find a good explanation of the gravity waves related to clouds with some examples. I hope you like it.
Hans
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Hello Don, gravity waves are certainly not restricted to nacreous and noctilucent clouds. It was the context in which I found the first explanation of gravity waves. They are just two – amybe extreme – examples. Here is another link that gives clear explanations – including examples of the way gravity waves are induced – for the lower clouds: Gravity waves.
Examples of non-garvity waves are a lot of undulatus appearances we are used to in our troposphere. They are in most cases the result of shearing winds with different speeds. Here is part of the text about undulatus form the Resources entry of the menu on the CAS site:
“Undulatus usually forms when the air above and below the cloud layer is moving at differing speeds and/or in different directions. It is the shearing effect of the two airstreams that gives rise to the cloud billows, which form perpendicular to the wind direction and can resemble ripples on a sandy beach caused by the movement of water.”
Best wishes, Hans
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Yes, Don, forgive me for saying so, but you missed something big. The striations you see on the CAD of 23d of June are in a shelf cloud. They are explained very well in a very different way. The situations of the clouds where gravity waves were mentioned and the situation of the shelf cloud, are not the same at all.
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This is what I based my ‘striation’ post on :
(from CAD explanation) – It forms as cool air dragged down. . . . lifting up the warmer, humid air near the surface
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The distinct and dramatic striations were likely due to the low air lifted by the winds flowing out from the storm consisting of alternating moister and drier layers.
I interpreted these to mean an up and down motion perpendicular to the motion of the (in this case) storm, which, according to my understanding, is the essence of gravity waves.
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Thanks for explaining your thoughts Don. It is fun to discuss things this way. For me your explanation proofs that there are so many interpretations possible, but I still think the situation of the first CAD you refereed to – and in which gravity waves were mentioned – is very different from the one with the shelf cloud. I think that the processes in a cumulonimbus producing a shelf cloud on its front involve much more power and different forces than the processes involved with the relatively more gently formed gravity waves. Who will know?
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Hans – I enjoyu this very much too, especially when I can (at least try to) learn something from someone with your experience.
You mentioned that gravity waves are gentle.
I can see that the shelf cloud is formed by something powerful. Also, I assume, that the air around a cumulonimbus/shelf is not stable, therefore requiring something sufficiently powerful to cause the observed striations.
Many articles on gravity waves use water as an example. Tossing a rock into a calm pond of water will produce waves. So will an underwater earthquake. The first is gently (gravity waves) and the second is a tsunami – I would not call this gentle, and even though the wave(s) exhibit an up-and-down motion, neither would I put that in the same category as the rock-in-the-pond wave.
Thank you for your insight!!!!
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I enjoyed reading this conversation – it’s cleared up the same question in my own head so thank you. As a one time science teacher I feel obliged to point out that Einstein’s waves are called ‘gravitational waves’ – and yes, completely different to gravity waves.
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