Geophysical Research Letters

On the influence of sea-ice inhomogeneities onto roll convection in cold-air outbreaks

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Abstract

[1] In this study we use large-eddy simulations (LES) to model roll convection within the convective atmospheric boundary-layer (CBL) during strong cold-air outbreaks (CAO). Previous LES were mostly unsuccessful in reproducing clear signals of roll convection, especially in case of strong surface heating and weak vertical wind shear in the CBL. In nature however, this phenomenon is very robust and roll convection can be observed as cloud streets in satellite pictures of almost any CAO. Previous LES studies assumed homogeneous sea-ice, unlike the current study, where under strong surface heating clear signals of rolls appear only when introducing sea-ice inhomogeneities in the marginal ice zone. For weaker surface heating, rolls also appear without sea-ice inhomogeneities. The results of this study suggest that in case of strong surface heating and weak vertical wind shear surface inhomogeneities increase the chance of roll formation.

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