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Abstract:
The representation of Arctic mixed-phase clouds - their formation, evolution as well as persistence – is still rather uncertain in coarse-scale regional models. In order to first evaluate and potentially improve the respective microphysical parameterizations, a more detailed process understanding becomes necessary. We performed several simulations at hectometer scale – and by that approaching cloud-resolving scales – around different observational supersites, which are equipped with remote sensing instrumentations for cloud observations. We used the ICON model in a large-eddy configuration on a limited area domain, allowing heterogeneous surface as well as lateral boundary conditions. And we applied a two-moment microphysics parameterization, but no cloud fraction parameterization. By simulating several days, the representation of mixed-phase clouds could be compared to the supersite observations and investigated in a statistical way. While the model shows a great potential in capturing the general structure and timing of mixed-phase clouds – especially at Ny-Ålesund (Svalbard) – we will also discuss existing sensitivities and uncertainties e.g. with respect to ice-formation processes, which led to too many simulated ice clouds. Beyond the detailed microphysical aspects, another uncertainty in the Arctic comes from the uncertain surface properties, especially over sea-ice. To tackle this question and to estimate the sensitivity, we simulated and compared our model simulations at different places across the Arctic. As a second aspect, we will show the influence of different surface and large-scale conditions on the representation of Arctic mixed-phase clouds and point out potential issues to be considered and improved especially in coarse-scale simulations.
