Abstract
The growth of liquid‐water droplets upon condensation nuclei as the relative humidity rises from 80 per cent to 100 per cent is examined. It is assumed that the condensation nuclei consist of sea‐salt particles and that the droplets are always in instantaneous equilibrium with the ambient relative humidity. An arbitrary nucleus‐size distribution formula, which is easily adjusted to fit an intuitively reasonable size distribution, is also assumed. It is found that the shape of the nucleus‐size distribution curve has very little effect upon the computed value of the liquid‐water content W of the fog though at saturation W varies as the square root of the mean mass of the nuclei. In near‐saturation conditions a small variation in relative humidity has a big effect upon W.
A formula for drop‐size distribution in fog at saturation is developed and found to agree with measurements.
Visibility in the developing fog is briefly considered and it is shown that Koschmieder's formula, applied to the growing water drops, leads to results consistent with experience. Neither the mean nucleus mass nor the shape of the nucleus‐size distribution curve affect the visibility at saturation.