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Gravity waves? The way you described this in your other post as "in which the air column itself is transported vertically", did you mean pressure waves, as in a

by dvtrn 5y ago

Gravity waves? The way you described this in your other post as "in which the air column itself is transported vertically", did you mean pressure waves, as in a change in air pressure? I'm not a geologist, so don't take my incredulity for anything suggesting scientific fact, here.

cjensen 5y ago
Wikipedia has the 'splainer for you[1]. There are good satellite examples online[2] But basically it has to do with buoyancy. A cloud or other layering of the atmosphere has a stable place in the vertical column. If the atmosphere passes over a mountain range that displaces the column vertically, the column returns to its normal position. In returning, the atmosphere overcorrects repeatedly and "bounces" back into position much like a single jump onto a mattress. [1] https://en.wikipedia.org/wiki/Gravity_wave https://en.wikipedia.org/wiki/Gravity_wave [2] https://twitter.com/ggweather/status/1427061411604099077 https://twitter.com/ggweather/status/1427061411604099077
- dvtrn 5y ago
  The mattress analogy was perfect and brought about the “aha” realization, so thanks for that!
dredmorbius 5y ago
I'm not a geologist (or meteorologist) either, so salt accordingly. One 'splainer I've seen[1] described the volcanic erruption as the result of seawater infiltrating a magma chamber or vent, flash-vaporising, and basically blowing straight up to a height of about 30km (roughly 100,000 ft). Think of this not simply as a pressure wave blasting upwards, but as a bolus of air (and steam / water vapour) punching up through the atmosphere. It's analogous to a water wave spiking up out of fluid --- after it rises up, it will collapse back down, then rebound up, repeating this several times. The spike also both propogates out and creates a gravity-wave front which propagates outward, again creating a vertical wave across the top of the atmosphere. We're used to gravity waves in water largely because water isn't compressible. Sound travels through water, but shock waves tend to have limited reach since water itself doesn't compress --- a water shock is rapidly transformed into a water gravity wave, with a surge and collapse. (How much energy is transmitted through either wave mode I don't know, though someone versed in fluid dynamics could probably say.) Air is compressible, so a major part of the effect of an explosion is shock. That said, you can get gravity waves in air as well, and the Tonga erruption is apparently a demonstration of this. ________________________________ Notes: 1. Possibly GeologyHub on YT: https://yewtu.be/channel/UCYeGh5VML5XPr5jYnzh3J6g https://yewtu.be/channel/UCYeGh5VML5XPr5jYnzh3J6g Though I've been viewing / reading many sources. Update: found it here: https://yewtu.be/watch?v=YcCkQaLkfxA https://yewtu.be/watch?v=YcCkQaLkfxA

by dvtrn 5y ago

cjensen 5y ago

Wikipedia has the 'splainer for you[1]. There are good satellite examples online[2] But basically it has to do with buoyancy. A cloud or other layering of the atmosphere has a stable place in the vertical column. If the atmosphere passes over a mountain range that displaces the column vertically, the column returns to its normal position. In returning, the atmosphere overcorrects repeatedly and "bounces" back into position much like a single jump onto a mattress. [1] https://en.wikipedia.org/wiki/Gravity_wave https://en.wikipedia.org/wiki/Gravity_wave [2] https://twitter.com/ggweather/status/1427061411604099077 https://twitter.com/ggweather/status/1427061411604099077

dvtrn 5y ago
The mattress analogy was perfect and brought about the “aha” realization, so thanks for that!

dredmorbius 5y ago

I'm not a geologist (or meteorologist) either, so salt accordingly. One 'splainer I've seen[1] described the volcanic erruption as the result of seawater infiltrating a magma chamber or vent, flash-vaporising, and basically blowing straight up to a height of about 30km (roughly 100,000 ft). Think of this not simply as a pressure wave blasting upwards, but as a bolus of air (and steam / water vapour) punching up through the atmosphere. It's analogous to a water wave spiking up out of fluid --- after it rises up, it will collapse back down, then rebound up, repeating this several times. The spike also both propogates out and creates a gravity-wave front which propagates outward, again creating a vertical wave across the top of the atmosphere. We're used to gravity waves in water largely because water isn't compressible. Sound travels through water, but shock waves tend to have limited reach since water itself doesn't compress --- a water shock is rapidly transformed into a water gravity wave, with a surge and collapse. (How much energy is transmitted through either wave mode I don't know, though someone versed in fluid dynamics could probably say.) Air is compressible, so a major part of the effect of an explosion is shock. That said, you can get gravity waves in air as well, and the Tonga erruption is apparently a demonstration of this. ________________________________ Notes: 1. Possibly GeologyHub on YT: https://yewtu.be/channel/UCYeGh5VML5XPr5jYnzh3J6g https://yewtu.be/channel/UCYeGh5VML5XPr5jYnzh3J6g Though I've been viewing / reading many sources. Update: found it here: https://yewtu.be/watch?v=YcCkQaLkfxA https://yewtu.be/watch?v=YcCkQaLkfxA