Parameterization of ice crystal aggregation

This thesis develops an ice aggregation parameterization scheme for Numerical Weather Prediction models. It incorporates ice crystal terminal fall velocities and cross-sectional areas which depend on air temperature.; The aims of this thesis are (i) to determine the effects of temperature on the aggregation rate of cloud ice crystals by snow aggregates, and (ii) to quantify the effects of snow aggregate size distributions of the same mass, but varying in broadness, on the collection rate. The results show that for subfreezing conditions the ice aggregation rate increases with increasing temperature. The effects of size distribution on collection rate can be shown by assuming snow aggregate size distributions are of the same mass but varying in broadness. The results indicate size distributions consisting of a greater number of larger particles result in a faster aggregation rate.