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Can wind/air that is moving at average speeds be slowed down by the cause of Friction? Also, Can Air bubbles in water be slowed down because of Friction? Please cite your sources.

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    $\begingroup$ I’m voting to close this question because cross posted on SE Astronomy, with an accepted answer: Can air/gas be slowed down by friction $\endgroup$
    – Fred
    Feb 26 at 20:35
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    $\begingroup$ This is much more on-topic here than at Astronomy.SE. $\endgroup$ Feb 27 at 1:14
  • $\begingroup$ Now that the duplicate on Astronomy.SE has also been closed as off-topic (appropriately so),I am voting to reopen this question here, which is where it belongs. To the OP: Do not cross-post. $\endgroup$ Feb 27 at 17:37
  • $\begingroup$ While I don't think it's off topic, it's so trivial that it should be answerable by the most basic observation, e.g. wind close to the ground or in trees is slower than at higher altitudes. $\endgroup$
    – jamesqf
    Mar 1 at 4:13
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Air is affected by friction. A brief search of AMS journals shows over 14,000 times friction is mentioned. How it is manifested in the equations that describe the atmosphere is complicated.

Let's think of wind as 'air moving' or perhaps space moving which air occupies. At some point, called the roughness length, the wind is 0 m/s (or knots or mph). If such a thing does not exist, then the earth would move with the wind (which is legitimate thing with blowing dust/snow). Concerning this, the atmosphere produces a frictional torque on the earth, and vice-versa. A metric to gauge the influence of friction is the friction velocity. Perhaps, most notably, friction is a major cause on why the surface wind and geostrophic wind are not the same.

Regarding air bubbles in water, I would say it has some effect, but is probably not the dominant effect. That is, unless you consider viscosity to be a manifestation of friction (which it is). If you consider viscosity to be a form of friction, then air has friction within itself. Viscosity is often considered to be so small that it is ignorable, unless you are dealing with micrometeorology or ocean dynamics (see Ekman transport). But even in micrometeorology, the few times true viscosity (not eddy viscosity) is not ignorable is within the dissipation of turbulent kinetic energy.

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