Evaporation rates

[chem geek]

Does water evaporate faster when the relative humidity is lower ?

Yes.

Of course, I might anticipate your next question which is how much faster does water evaporate as a function of the level of relative humidity. As a first approximation and with temperature, air density, and air flow (i.e. wind) held constant, the rate of evaporation is inversely proportional to the relative humidity (RH). So the rate is highest (say, 1.0) with 0% RH and is 10% lower (say, 0.9) at 10% RH, half the rate at 50% RH, 90% lower (say, 0.1) at 90% RH and is 0 (i.e. no evaporation) at 100% RH.

Richard