The effect of microphysical and environmental factors on the development ofprecipitation in warm idealised cloud is explored using a kinematic modelling framework.A simple one-dimensional column model is used todrive a suite of microphysics schemes including a flexible multi-moment bulkscheme (including both single and dual moment cloud liquid water) and astate-of-the-art bin-resolved scheme with explicit treatments of liquid andaerosol. The Factorial Method is employed to quantify and compare thesensitivities of each scheme under a set of controlled conditions, in orderto isolate the effect of additional microphysical complexity in terms of theimpact on surface precipitation. At relatively low updraught speeds, the sensitivity of thebulk schemes was found to depend on the assumptions madewith regards the treatment of droplet activation. It was possible to achieve a much closer agreement betweenthe single and dual moment bulk schemes by tuning the specified droplet number concentrationin the single moment scheme, suggesting that a diagnostic representation of droplet number may be anacceptable alternative to the more expensive prognostic option.However the effect of changes in CCN concentration were found toproduce a relatively stronger effect on precipitation in the bulk schemes compared to the bin scheme;this is believed to be a consequence of differences in the treatment of drop growthby collision and coalescence. Collectively, these resultsdemonstrate the usefulness of the Factorial Method as a model development tool forquantitatively comparing and contrasting the behaviour of microphysicsschemes of differing levels of complexity within a specified parameter space.
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