Multi-event analysis of the westerly Greenland tip jet based upon 45 winters in ERA-40
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2009
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Journal Article
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Abstract
The westerly Greenland tip jet is an intense, narrow and intermittent wind phenomenon located southeast of Cape Farewell that occurs frequently during the winter season. Using the ERA‐40 reanalysis dataset, a catalogue of 586 objectively detected westerly tip jet events is compiled for the winters 1957‐2002, and an analysis is undertaken of the character of the jet and its accompanying atmospheric features. It is shown that the tip jet frequency exhibits a significant positive correlation with both the NAO index and the latitude of the Icelandic Low. The peak wind speed and accompanying heat fluxes of the jet have values up to 30 m s⁻¹and 600 W m⁻², respectively, and are sustained for less than one day. The air parcels constituting the tip jet are shown, based upon a trajectory model and the ERA‐40 dataset, to have a continental origin, and to exhibit a characteristic deflection and acceleration around southern Greenland. The events are almost invariably accompanied both by a notable coherence of the lower‐level tip jet with an overlying upper‐level jet stream, and by a surface cyclone located to the lee of Greenland. It is also shown that the cyclone originates upstream of and is advected to the lee of Greenland, and thereby it both precedes in time and contributes dynamically to the formation of the tip jet. On this basis, it is suggested that the tip jet arises from the interplay of the synoptic‐scale flow evolution and the perturbing effects of Greenland's topography upon the flow. Copyright © 2009 Royal Meteorological Society
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published
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Journal / series
Volume
135 (645)
Pages / Article No.
1999 - 2011
Publisher
Wiley-Blackwell
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Subject
cyclone; jet stream; Irminger Sea; Greenland; tip jet
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Received 22 January 2009, Revised 3 July 2009, Accepted 6 July 2009, Article first published online 5 October 2009.