Large-eddy simulation of the turbulent flow around RV Polarstern during MOSAiC

The Arctic is an early warning system for climate change and has a tremendous influence on our climate. Despite the importance of understanding Arctic climate change, scientists still struggle to understand the reasons and consequences of current rapid Arctic warming. Thus, the MOSAiC campaign took place in the years 2019 and 2020. The German research vessel (RV) Polarstern spent one year drifting, trapped in the ice, through the Arctic Ocean. A network of research camps was formed surrounding the RV Polarstern. The network offered various teams the opportunity to monitor and investigate the ocean, ice, atmosphere, and life in the Arctic winter. One driving uncertainty of atmospheric observations around the RV Polarstern is the effect of ship-induced wakes on in-situ measurements during MOSAiC. Quantification of these effects is key to ensure the MOSAiC data quality.

Results from a large-eddy simulation study using the model PALM are presented to assess the wake effects of RV Polarstern for selected days of the MOSAiC campaign. By using very small grid spacings in the order of a few meters, we are able to resolve the ship's envelope as an obstacle to the flow. We first conduct a grid sensitivity study to illustrate how the wake flow depends on model resolution. In a second step, we present a set of simulations to study the effect of ship-induced wakes on the turbulent flow. For this purpose, we investigate not only different angles of attack and wind speeds, but also different stability regimes. We analyze how far ship-induced wake effects propagate and demand consideration in data analysis.