Outputs for Köhler Calculations

The results of the calculations consist of saturation values and particle water contents and other properties as a function of particle radius. They are either output sequentially to the screen (column output), or can be plotted as graphs (not yet implemented). If graphical output is selected, a new page will open containing lists of x and y variables for plotting. The results can also be downloaded as a "comma separated value" (csv) file which can be read by Excel and other programs. The link to this file is displayed near the top of the page containing the column output.

Notes describing the meanings of each of the column headers are printed at the bottom of each output page, as is the size and composition of the dry particle used to determine hygroscopic growth factors and κ (kappa) values (E-AIM calculations only).

The assumed geometry of the particle is "core-shell": a spherical core containing any solid salts that have formed, surrounded by a shell of aqueous solution.

Column Output

This includes the following information:

First, the peak supersaturation (critical supersaturation Sc) is identified and its value determined by interpolation of the tabulated results. The following characteristics of the particle at Sc are listed: the value of Sc; the particle radius, liquid water content, density, and surface tension; and the the partial molar volume of water in the particle. All units are SI, so that these numbers can be used together with R (8.3144 J K−1 mol−1) and T to calculate the influence of surface curvatiure on the saturation vapour pressure of the aqueous particle (the Kelvin effect).

The peak value will still be listed if the particle is large enough that the peak equilibrium RH above the particle, i.e. the highest value of S in the column of results in this page, is less than unity (or 100%).

In calculations where E-AIM is used to determine the properties of particles (all types of input except "Particle radius, and volume fractions of solids (κ - K√∂hler)") all of the particle properties, and its equilibrium state, are calculated using E-AIM. The value of the saturation S is calculated using the Kelvin equation, as described on the methods page. The model outputs are as follows:

In calculations where the κ - Kölher equation is used to determine the properties of particles, the outputs are similar to those from E-AIM. The main differences are listed below:

Graphical Output

This has not been implemented yet.

References

(1)  M. D. Petters and S. M. Kreidenweis (2007) A single parameter representation of hygroscopic growth and cloud condensation nucleus activity. Atmos. Chem. Phys. 7, 1961-1971.