Condensation and evaporation of water vapor in mixed aerosols of liquid droplets and ice: numerical comparison of growth rate expressions

We compare four different H2O mass flux descriptions in simulations of the evolution of mixed water/ice aerosol populations undergoing condensational growth. It is shown that the Maxwellian description, ignoring condensation heat release, overestimates the growth rates severely when compared with an exact numerical description. The well-known Mason equation predicts the gr owth rates somewhat better, but still in an inadequate manner as far as clo ud drop formation is considered: after 100 s growth the drop radii are over estimated by up to a factor of 3 at -30 degreesC, An analytical mass flux f ormulation by Lehlinen et al. (1998) (J, Aerosol Sci. 29, 1035), on the oth er hand, compares very well with the exact description while requiring only one percent of computing time needed for the exact numerical calculations. (C) 2001 Elsevier Science Ltd. All rights reserved.