Naked Science Forum
Life Sciences => The Environment => Topic started by: krytie75 on 15/09/2009 00:46:05
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I was watching some fast moving clouds passing over head the other day and I noticed something which I realised had been obvious my whole life. Clouds always seem to move as one 'solid' block with a specific shape. Now surely if my understanding of the way the atmosphere moves is correct, clouds should be being battered with little gusts and spirals of air all the time. The effect would seem to be bigger still if one imagines how quickly wind speed can change when out in fierce weather.
So my question is - Why do clouds maintain their form rather than being blown around and spread out by the winds that are moving them?
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Clouds don't maintain their form. If you sit and watch or better still record a cumulus cloud on a fair calm day you will see currents rising and falling in the cloud like a water fountain. This will be most visable around the tops and edges.
Depending on the strength of the wind you will also see the "tales" of cirrus cloud being pushed further back in to a hook form and also getting longer.
Clouds also move from one layer to another, getting lower, thicker and changing their shape and form. For example: stratocumulus can develop on to stratus, nimbostratus more often than not forms from altostratus
One cloud form that does generally keep it's shape is altocumulus lenticularis:
http://www.metoffice.gov.uk/publications/clouds/cm4/
Meteorological Office fact sheet on clouds
http://www.metoffice.gov.uk/corporate/library/factsheets/factsheet01.pdf
Time lapse imagery
http://www.motionelements.com/stock-video-footage/119802/single-cell-cumulonimbus-cloud.html
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Ok, this I will accept, thank you for your answer SkepticSam. Clouds do change but, you have to observe them for some time to see this. My revised question, hence, is Why aren't clouds stirred around and mixed up as much as I think they should be, by fast winds and the turmoil of micro wind systems? You know what I mean.
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I think you may be refering to Convective / cumulus clouds. Try these time lapse files http://mesonet.agron.iastate.edu/cool/ . You can observe cumulus clouds moving, expanding and changing shape in a matter of minutes. These are stirred around by convection currents and moved along by the wind.
This is different for layered cloud. They form in a stable environment so there is no stirring. You can still watch their changing shape and form as they move. Does this answer your questions?
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Ok, this I will accept, thank you for your answer SkepticSam. Clouds do change but, you have to observe them for some time to see this. My revised question, hence, is Why aren't clouds stirred around and mixed up as much as I think they should be, by fast winds and the turmoil of micro wind systems? You know what I mean.
I think,
At higher altitudes, I believe that the wind is much more uniformed, compared to the ground. Therefore, the clouds won't scatter much.
...I think...
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Clouds do not get torn apart by the wind because they are embedded in it. The changes in shape happen more in the vertical direction do to convection (vertical transport of air due to heat), or lack thereof. You may notice a cloud tend to roll horizontally due to friction within the boundary layer (first 3-6 km of the atmosphere). The wind closer to the surface of the earth has less magnitude then the wind aloft. And becasue the clound cannot extend beneath its base, the wind aloft forces it over on itself; much like you rolling a pencil across a table top with the palm of your hand. Clear as mud?