SURFACE KINETIC LIMITATION OF ICE CRYSTAL-GROWTH IN THE STRATOSPHERE

Formulae describing the growth of polar stratospheric ice crystals are described. These take account of the bulk supersaturation and radiative heat transfer, heat conduction, mass diffusion and surface kinetic processes at the air/crystal interface. Surface phenomena are not usually considered in models of ice crystal growth derived from those used to study liquid droplets. Numerical solutions for the case including surface kinetics demonstrate that it can be the major rate-limiting process for small particles at low supersaturations. Results are also shown for the case of large nitric acid trihydrate (NAT) particles when growth is limited by the rate of diffusion of nitric acid vapour to the crystal surface. The behaviour of NAT in these circumstances is similar to that of water ice.