Figure 2. . Particles respond to changes in the surrounding relative humidity of the gas phase by absorbing water and growing in size.

Here, the growth in size is represented as a diameter growth factor which reports the change in particle size relative to the dry particle as the relative humidity increases. Growth curves for particles of increasing hygroscopicity parameter (= 0.01, 0.12 and 1.27) are shown as examples of insoluble, low solubility and high solubility, respectively.