How the representation of microphysical processes affects tropical condensate in a global storm-resolving model

Abstract. Cloud microphysics are a prime example of processes that remain unresolved in atmospheric modelling with storm-resolving resolution. In this study, we explore how uncertainties in the representation of microphysical processes affect the tropical condensate distribution in a global storm-resolving model. We use ICON in its global storm-resolving configuration, with a one- or a two-moment microphysical scheme and do several sensitivity runs, where we modify parameters of one hydrometeor category of the applied microphysics scheme. Differences between the one- and the two-moment scheme are most prominent in the partitioning of frozen condensate in cloud ice and snow, and can be ascribed to the habit's definition for each scheme which is associated with different process rates. Overall differences between the simulations are moderate and tend to be larger for individual condensate habits than for more integrated quantities, like cloud fraction or total condensate burden. Yet, the resulting spread in the tropical energy balance of several W m^-2 at the top of the atmosphere and at the surface is substantial. Although the modified parameters within one scheme generally affect different process rates, most of the change in the condensate amount of the modified habit and even total condensate burden can be attributed to a single property, the change in fall speed. Tropical mean precipitation efficiency is also well explained by changes in the relative fall speed across different habits and both schemes.