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I have read that air in tropical regions is more humid because, as the temperature increases, the entropy of air is bigger and so it is easier for water to disperse and diffuse.

How does this mechanism work at the microscale? I still can't see why higher entropy makes the air more humid.

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  • $\begingroup$ Can you confirm whether you mean higher temperature causes higher humidity or higher temperature allows higher humidity? $\endgroup$
    – bendl
    Commented Oct 24, 2017 at 12:27
  • $\begingroup$ Hotter air can hold more water in vapor phase as explained by Clausius-Clapeyron equation, are you asking of an intuitive explanation of this? $\endgroup$
    – Communisty
    Commented Oct 24, 2017 at 12:41
  • $\begingroup$ @Communisty Yes, what is the intuition behind this $\endgroup$
    – veronika
    Commented Oct 24, 2017 at 12:53

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The water mixed in air naturally wants to always be in the lowest energy state. To break away from a liquid surface the water molecule needs energy to escape the surface tension force. If there is a lot of water in the air in gas phase then by chance they will be hitting the liquid surface more often and changing into liquid too. The air is saturated by water when these two competing actions are in balance. When the temperature is higher the single molecules in liquid have a higher chance of surpassing the surface tension and turning into gas. Thus in warmer temperatures the balance is reached only when more water is present.

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  • $\begingroup$ So, in my eyes, this is not really a property of air then. It is more the transition from liquid to gas itself. $\endgroup$
    – Ben
    Commented Jul 8, 2020 at 8:48

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