3
$\begingroup$

Clouds are present in the troposphere . So the radiation from the Sun first needs to pass this layer of the atmosphere to come down which means that the clouds above are constantly being radiated from the Sun in daytime with higher intensity than what reaches down the earth but if that's true why don't the clouds gradually evaporate and just never condense to form clouds again (because of higher radiation intensity as we go above the Earth's surface).

What exactly makes clouds stable as a large lump even if they are constantly being radiated at higher intensity of sunlight from above ?

Edit :

As per Joseph's answer , the infrared back from the Earth heats the atmosphere. But Wikipedia says that enter image description here . So if it's true then why don't the vapours above absorb the infrared from the Sun directly without letting it pass through in the first place ?

Why aren't the clouds affected by infrared from Sun if they are affected by infrared from Earth ?

$\endgroup$
1
  • 1
    $\begingroup$ Discussed here & here. $\endgroup$
    – J.G.
    May 26 at 7:28
4
+50
$\begingroup$

Light from the sun heats the earth’s surface, which in turn heats the atmosphere.

The atmosphere is made up of air and water vapour etc (when that vapour is thick enough we get clouds). The light coming from the sun is reflected back into space by clouds, and some light completely passes through them (though there is some scattering but this on its own is not significant enough to cause the evaporation of clouds). You will notice that clouds are bright white on their tops and darker on their opposite surface.

What does heat up the atmosphere is sunlight striking/heating the earth’s surface. It is this (infrared radiation) that heats gases and vapours in the atmosphere. So it basically comes down to things like temperature, pressure, humidity, wind conditions etc that will determine if clouds fully form (precipitation next) or dissipate.

$\endgroup$
9
  • $\begingroup$ thanks for ur answer .. but I don't get this :**light from sun heats the earth's surface...**. Why does the radiation cause no effects when coming towards the earth in the first place ? $\endgroup$
    – Ankit
    May 26 at 7:42
  • 1
    $\begingroup$ Yes. It heats the earth’s surface since the surface absorbs the suns light. The earth’s surface then radiates infrared light ( as heat). $\endgroup$
    – joseph h
    May 26 at 7:45
  • 1
    $\begingroup$ woahh.. and the clouds Don't absorb much of the heat ? $\endgroup$
    – Ankit
    May 26 at 7:49
  • $\begingroup$ That is correct. They reflect/scatter a majority of sunlight. $\endgroup$
    – joseph h
    May 26 at 8:03
  • $\begingroup$ en.m.wikipedia.org/wiki/Electromagnetic_absorption_by_water read the statement about absorption spectrum for vapours first para . $\endgroup$
    – Ankit
    May 26 at 14:18
0
$\begingroup$

I assume you mean to ask Why cloud don't evaporate?

First,

How clouds are formed?

Assuming a hot sunny day with clear sky, water on surface of a water body evaporates. Assuming still air evaporated water remains at same site. Till now it is in gaseous state. Now, As Sun is going down condition for condensation are getting favorable so evaporated water condense on the small dust particle. It is some sort of chain reaction. One drop is condensed now drops condense on first one and so on. This gives a cloud.

Now I think as this would have had released a lot of energy, It would take same lot of energy rather more than that to undo the process. Clouds don't cover whole sky. Due this the probability of enough amount of energy from solar radiation decreases drastically to undo the condensation process. Moreover disintegration of clouds by providing heat violates 2nd Law of Thermodynamics. Solar radiation do change physical configuration of clouds but can never disintegrate it. And there can be never enough clouds to block all of solar infrared radiation.

$\endgroup$
1
  • $\begingroup$ Thanks for ur answer . But why would the disintegration violate Second law of thermodynamics ? $\endgroup$
    – Ankit
    Jun 5 at 18:41

This site is temporarily in read only mode and not accepting new answers.

Not the answer you're looking for? Browse other questions tagged .