Why don't clouds gradually evaporate and never come down as rain? 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

The absorption in the gas phase occurs in three regions of the spectrum. Rotational transitions are responsible for absorption in the microwave and far-infrared, vibrational transitions in the mid-infrared and near-infrared. Vibrational bands have rotational fine structure. Electronic transitions occur in the vacuum ultraviolet regions.
Liquid water has no rotational spectrum but does absorb in the microwave region. Its weak absorption in the visible spectrum results in the pale blue color of water.

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 ?
 A: 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.
A: 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.
A: Clouds do evaporate when the temperature and irradiation is high enough, but only to condense again at greater height where the temperature is lower.
