Abstract
Wintertime cold air outbreaks along a non-frozen sea channel or a long lake can become destructive if the related bands of heavy snowfall hit onto land. The forcing for such bands is studied with a 2D numerical model set across an east–west sea channel at 60oN (‘Gulf of Finland’), varying the basic geostrophic wind V g. Without any V g opposite coastal land breezes emerge with convergence. This results in a quasi-steady rising motion w max ~ 7.5 cm/s at 600 m in the middle of the gulf, which can force a snow band. During weak V g, the rising motion is reduced but least so for winds from 60o to 80o (~ENE), when modest alongshore bands could exist near the downstream (Estonian) coast. During V g of 4–6 m/s from any direction, the land breezes and rising motions are reduced more effectively, so snow bands are not expected during moderate basic flow. In contrast, during a strong V g of 20–25 m/s from 110o to 120o (~ESE) the land breeze perturbations are intense with w max up to 15–18 cm/s. The induced alongshore bands of heavy snowfall are located in these cases at the sea but quite close to the downstream (Finnish) coast. They can suddenly make a landfall if the basic wind turns clockwise.
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Acknowledgements
H. Savijärvi is grateful to Sami Niemelä and Timo Vihma for the Fig. 1 material and fruitful discussions. The anonymous reviewers are thanked for their comments that improved the article.
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Savijärvi, H. Cold air outbreaks along a non-frozen sea channel: effects of wind on snow bands. Meteorol Atmos Phys 127, 383–391 (2015). https://doi.org/10.1007/s00703-015-0370-8
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DOI: https://doi.org/10.1007/s00703-015-0370-8