parcel_model.thermo.kohler_crit¶

parcel_model.thermo.kohler_crit(T, r_dry, kappa, approx=False)¶

Critical radius and supersaturation of an aerosol particle.

The critical size of an aerosol particle corresponds to the maximum equilibrium supersaturation achieved on its Kohler curve. If a particle grows beyond this size, then it is said to “activate”, and will continue to freely grow even if the environmental supersaturation decreases.

This function computes the critical size and and corresponding supersaturation for a given aerosol particle. Typically, it will analyze Seq() for the given particle and numerically compute its inflection point. However, if the approx flag is passed, then it will compute the analytical critical point for the approximated kappa-Kohler equation.

Parameters:

T : float

ambient air temperature, K

r_dry : float

dry particle radius, m

kappa : float

particle hygroscopicity parameter

approx : boolean, optional (default=False)

use the approximate kappa-kohler equation

Returns:

(r_crit, s_crit) : tuple of floats

Tuple of \((r_\text{crit},\, S_\text{crit})\), the critical radius (m) and supersaturation of the aerosol droplet.