Do cirrus clouds in the upper troposphere move faster than cumulus and stratus clouds in the lower atmosphere?
What about clouds associated with extratropical systems, compared with clouds in the tropics?
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asked Apr 15, 2014 at 19:15
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5$\begingroup$ You mean upper troposphere, not upper atmosphere. There are no cirrus clouds in the upper atmosphere (only noctilucent clouds). $\endgroup$– gerrit ♦Apr 15, 2014 at 19:31
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2 Answers
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Cloud particles are suspended in air, and their movement is governed by:
- Wind; whichever way the wind blows, the clouds go (with some exceptions such as lenticular clouds; thanks jamesqf comment). The wind is often strongest in the upper troposphere (there are no clouds in the upper atmosphere), so upper tropospheric clouds will move faster than near-surface clouds.
- Convection: strong updrafts will force particles upward, as will forced convection by wind reaching obstacles
- Particle size: larger particles are more likely to fall down. Note that "fall down" may be used either relative to the surrounding air, or relative to the ground (i.e. precipitation that may or may not reach the ground).
So the type of cloud is indirectly relevant: different cloud types are associated with different particle sizes, are to a larger or smaller degree the consequence of convection, and are more or less likely to contain precipitation-sized particles.
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$\begingroup$ Can you elaborate on the particle size part? What do you mean by fall down? Fall down as rain? And how does it affect cloud movement? $\endgroup$– GimelistNov 1, 2014 at 13:59
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4$\begingroup$ Re wind, usually but not necessarily. Consider lenticular clouds, which are stationary even though they are created by strong winds. $\endgroup$– jamesqfSep 20, 2017 at 17:30
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Upper atmospheric pressure is lower than surface pressure which entails higher elevation clouds will indeed move faster than lower elevation clouds which will move at slower speeds.
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3$\begingroup$ This answer would be improved with references $\endgroup$– FredSep 20, 2017 at 15:29
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$\begingroup$ Thinking that though less air means less air molecules to resist the movement, it also means less molecules to impart the push in the first place. As far as I understand it, the highest winds being near the top of the troposphere are more to do with the temperature profile than some fundamental effect of being at lower pressures. $\endgroup$ Sep 20, 2017 at 17:20