Fig. 6. Water activity across droplet radius as a 100 nm particle follows an updraft of 0.02, 0.2 and 2 m s–1 (left to right) with temperature decreasing according to the dry adiabatic lapse rate and fixed water vapour partial pressure. Droplets start in equilibrium with their surrounding RH at a homogeneous water activity of 0.2, at a temperature of 220, 230 or 240 K (top to bottom). The resulting changes in RH and temperature with time are shown in ESI Fig. 7.† The dotted lines indicate the point at which the RHice increases above 100% and heterogeneous nucleation is feasible.
