Collection/aggregation algorithms in Lagrangian cloud microphysical models: rigorous evaluation in box model simulations

Recently, several Lagrangian microphysical models have been developed which use a large number of (computational) particles to represent a cloud. In particular, the collision process leading to coalescence of cloud droplets or aggregation of ice crystals is implemented differently in various models. Three existing implementations are reviewed and extended, and their performance is evaluated by a comparison with well-established analytical and bin model solutions. In this first step of rigorous evaluation, box model simulations, with collection/aggregation being the only process , have been performed for the three well-known kernels of Golovin, Long and Hall