A Performance Baseline for the Representation of Clouds and Humidity in Cloud‐Resolving ICON‐LEM Simulations in the Arctic.

In the context of Arctic amplification many of the feedback mechanisms, decreasing or enhancing the warming, involve clouds and water vapor. Currently, there is a gap in understanding the role of clouds which leads to uncertainties in climate simulations. Modeling frameworks such as the ICOsahedral Non‐hydrostatic model (ICON) are used to understand the Arctic atmospheric processes as well as predict future changes. In this study, we challenge ICON in the large‐eddy setup (ICON‐LEM) by performing cloud‐resolving simulations over parts of Svalbard, including Ny‐Ålesund. We ran daily simulations over 5 months and analyzed the column above Ny‐Ålesund. The local supersite's observations enabled us to create a baseline for the model performance focusing on the representation of liquid water and water vapor. We narrow in on possibilities to improve the cloud microphysical representation based on statistical evaluations, not just single cases. We found an astonishing agreement between most of the analyzed variables. For instance, the model integrated water vapor showed only a low bias of 0.21 kg m−2. The number of cloudy days is slightly higher in the model (+4%). Further, we found that the model produces an unrealistically high number of pure ice clouds. Small to medium precipitation events are similar in amount and time but the number of strong precipitation events is underestimated. Further results are discussed and show that ICON‐LEM is a useful tool to study the Arctic. With this thorough analysis, we highlight the value of local cloud‐resolving simulations to understand changes in the Arctic atmosphere. Plain Language Summary: The Arctic is warming faster than the rest of the globe. Many atmospheric processes impact the rate of the warming. Explaining these processes is challenging. Especially processes involving clouds lack sufficient understanding. We can use computer models to answer some of our questions, but for that, the models must be good enough and we must know their limitations. In this study, we used several months of simulations for Svalbard which we created with the ICOsahedral Non‐hydrostatic (ICON) model. The simulations had a high resolution and we used a model specialized for that: The ICON Large‐Eddy model (ICON‐LEM). We analyzed how well the model can represent clouds and humidity. One result is that many clouds contained more ice than what was measured at that location. We also found that the model produced more clouds than were observed. On the other side, the water vapor amount and wind field were simulated relatively precisely. The results show that the ICON model is helpful to study the Arctic. The ability to analyze many cases made it possible to quantify some of the limitations in the creation and development of clouds and precipitation. Knowing these limitations will help us to improve the model in the future. Key Points: Cloud resolving simulations for several months using the ICOsahedral Non‐hydrostatic model Large‐Eddy model in the Arctic are evaluatedHigh agreement of model and observations on wind flow, integrated water vapor, and light to medium precipitationMore clouds are simulated than observed but at the same time the model clouds lack liquid water [ABSTRACT FROM AUTHOR]