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A Model-Based Climatology of Low-Level Jets in the Weddell Sea Region of the Antarctic

  • Low-level jets (LLJs) are climatological features in polar regions. It is well known that katabatic winds over the slopes of the Antarctic ice sheet are associated with strong LLJs. Barrier winds occurring, e.g., along the Antarctic Peninsula may also show LLJ structures. A few observational studies show that LLJs occur over sea ice regions. We present a model-based climatology of the wind field, of low-level inversions and of LLJs in the Weddell Sea region of the Antarctic for the period 2002–2016. The sensitivity of the LLJ detection on the selection of the wind speed maximum is investigated. The common criterion of an anomaly of at least 2 m/s is extended to a relative criterion of wind speed decrease above and below the LLJ. The frequencies of LLJs are sensitive to the choice of the relative criterion, i.e., if the value for the relative decrease exceeds 15%. The LLJs are evaluated with respect to the frequency distributions of height, speed, directional shear and stability for different regions. LLJs are most frequent in the katabatic wind regime over the ice sheet and in barrier wind regions. During winter, katabatic LLJs occur with frequencies of more than 70% in many areas. Katabatic LLJs show a narrow range of heights (mostly below 200 m) and speeds (typically 10–20 m/s), while LLJs over the sea ice cover a broad range of speeds and heights. LLJs are associated with surface inversions or low-level lifted inversions. LLJs in the katabatic wind and barrier wind regions can last several days during winter. The duration of LLJs is sensitive to the LLJ definition criteria. We propose to use only the absolute criterion for model studies.

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Author:Günther Heinemann, Rolf Zentek
Parent Title (English):Atmosphere
Place of publication:Basel
Document Type:Article
Date of completion:2021/12/07
Date of publication:2021/12/07
Publishing institution:Universität Trier
Contributing corporation:The publication was funded by the Open Access Fund of Universität Trier and the German Research Foundation (DFG)
Release Date:2022/05/04
Tag:Antarctic; inversion; katabatic winds; low-level jets; stable boundary layer
GND Keyword:Atmosphärische Grenzschicht; Inversion; Katabatischer Wind; Modellierung; Strahlstrom; Weddellmeer
Volume (for the year ...):2021
Issue / no.:Band 12 (2021)
Number of pages:20
Institutes:Fachbereich 6 / Raum- und Umweltwissenschaften
Dewey Decimal Classification:9 Geschichte und Geografie / 90 Geschichte / 900 Geschichte und Geografie
Licence (German):License LogoCC BY: Creative-Commons-Lizenz 4.0 International

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