Microphysical sensitivities in global storm-resolving simulations

In global storm-resolving models (SRMs), that resolve convection explicitly instead of parameterizing it, microphysical processes are now fundamentally linked to their controlling factors, i.e., the circulation. While in conventional climate models the convective parameterization is one of the main sources of uncertainties (and a popular tuning parameter), this role might be passed on to the microphysical parameterization in global SRMs. In this study, we use a global SRM with two different microphysical schemes. For each scheme we do several sensitivity runs, where in each run we vary one parameter of the applied microphysics scheme in its range of uncertainty. We find that the two microphysics schemes have distinct signatures, e.g., in how condensate is partitioned between ice and snow. In addition, perturbing single parameters of each scheme also affects condensate amounts and hence the heat budget of the tropics. Among the parameters tested, the model is particularly sensitive to the ice fall speed and the width of the raindrop size distribution, which both cause several 10s W/m2 variation in radiative fluxes. Overall, microphysical sensitivities in global SRMs are substantial and resemble inter-model differences such as in the DYAMOND ensemble.