If clouds are water vapour then why does the vapour bunch together to form them?

Question

Why is it not an equally dispersed sheet in the sky? Either overcast or clear all the time?

Answer 1

It doesn't bunch together, in fact it normally is a rather uniform layer. However, what causes most puffy clouds is the vertical movement of the air.

Thermals are often quite small areas of rising air cause by heating of the earths surface. These small areas of vertical current will push a layer that is near saturation upward which decreases the temperature and achieves the saturation of the air to respect with water. When that happens, and there is continued vertical rise, cloud droplets will from the moisture that is above the saturated equilibrium level of water. The reason why it is not a whole sheet is the air has to be replaced below the updraft. Since nature will not allow a vacuum, there has to be descending air in the area around where the thermal is rising. In the case of descending air, the temperature is rising due to increasing pressure and thus the humidity is being lowered.

If there are clouds, in this zone, they likely will dissipate. The rapid clearing of clouds near a main updraft of a thunderstorm is one of the things that storm chasers are watching for. The sudden appearance of a strong downdraft near the updraft is a precursor to the formation of a tornado.

Answer 2

Clouds are made of water droplets or ice particles, not water vapour. Clouds form in regions of sky where the air temperature is below the dew point.

Water vapour is everywhere in the atmosphere - even the clear bits. In the clear bits the temperature is above the dew point.

Answer 3

Cloud formation is the result of a multiplicity of factors, some of which have been alluded to.

Firstly there needs to be water vapour suspended in the air. This can only occurr as a result of evaporation from over water bodies of sufficient significant size due to high radiant sun-light generated heat.

Next a nucleus of dust particles is necessary for the water vapour to bond to as a core to prevent the dissipation evenly as you describe. That the dust is present is readily shown by the fact that vehicles (and other exposed products) end up dirty -- not clean -- following a rain shower.

Due to the Earth's rugged terrain surface and varied composition, some areas reflect the Sun's radiant heat more readily than other areas. This creates some regions of greater evaporation over water and greater surface drying with resultant dust formation than elsewhere.

With the localised areas of increased heat radiation comes variations in the temperatures and air pressures (which help generate winds ) making bubbles within the air layers that surround the Earth. Some bubbles, due to their pressure, are better able to support greater volumes of suspended water than others.

Because of decreased air density with altitude as the air become thinner -- and there is reduced particle density, there exists less ability to contain water volume. The pressure/ heat bubbles may rise and fall between the air layers resulting in the pockets of water-laden air migrating vast distances from their origin.

When the water-laden air (clouds) ascend to sufficient altitude that the air is too thin to continue support, the clouds strike a terrestial feature that break the surface tension, the air pressure is changed by encountering a differing air pressure gradient or the cloud's molecular electrical bonding is disrupted by excessive imbalances in electrical charges (a storm) the air's water supportablity is broken. Rain occurs.

Many of these individual elements readily occur across the planet. However for a number of them to occur simultaeneously is rare and very localised. Water bodies not too distant from dust sources with moisture supporting air bubbles above are relatively few.
Urbanised industrialisation can increase water concencration bodies, radiant heat properties and suspended particulate matter (like pollutants) to produce more likely-hood of cloud formation.

However cloud supportability conditions are frequently changed before an even layer of overcast conditions are permitted to occur. This can frequently happen even before sufficient air/water saturation becomes visible as clouds.

Thus clouds remain essentialy localised phenomena.

Answer 4

I'd say its all to do with temperature, water molecules of the same tempreature whilst in vapour form would gather in areas of the same temperature, and as heat rises, warmer water molecules will collect at a higher altitude than cooler ones. wind has temperature too, a warm breeze or a cool breeze.a warm breeze will blow cooler water molecules slower because the cooler something is it contracts making the molecules more compact or denser. water vapour of a similar temp will be less compact and will travel easier on the breeze. I believe this is why we have thunder storms, large pockets of cold rain clouds battering against warm rainclouds conflicting temp and density. rapidly warming cold clouds and rapidly cooling warm clouds, will turn the vapours into such compact volumes of water, there fore resulting in rain......if this happens on a very hot day, it can charge the particles electonically, causing lightning, thunder is just the sound made by the lightning, simply hearing the thunder after the flash of lightening is because light travels faster than sound.
I dunno if this makes sense to any one else........but it does to me.

Answer 5

First, I'd disagree that clouds are water vapor. Water vapor is an invisible gas, so it is not what you see when you see clouds. You either see liquid water droplets or ice. You don't have clouds everywhere because some places are wet (like oceans) and some places are dry (like deserts) and the air in contact with those places takes on those characteristics, then it moves around and doesn't get well mixed.

Answer 6

a bit of dust starts a collection, and then surface tension and cohesion hold them together and help them grow larger.. wind shuffles the hole thing around and keeps them aloft until they become too heavy.

Answer 7

Atmospheric pressure.

Answer 8

wind pressure

Answer 9

because of surface tension and wind