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Gap flows: Results from the Mesoscale Alpine Programme

Mayr, Georg J. und Armi, Laurence und Gohm, Alexander und Zängl, Günther und Durran, Dale R. und Flamant, Cyrille und Gabersek, Sasa und Mobbs, Stephen und Ross, Andrew und Weissmann, Martin (2007) Gap flows: Results from the Mesoscale Alpine Programme. Quarterly Journal of the Royal Meteorological Society, 133, Seiten 881-895. DOI: 10.1002/qj.66

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Offizielle URL: http://www3.interscience.wiley.com/journal/113388514/home


An overview of advances in the observation, modelling, forecasting, and understanding of flows through gaps achieved in the Mesoscale Alpine Programme is given. Gaps are lateral constrictions of topography (level gaps) often combined with vertical terrain changes (passes). Of the possible flow configurations, only an asymmetric one (relatively deep and slow upstream, accelerating and thinning downstream), which connects two different reservoirs on each side of the gap, is examined. The flow is strongly nonlinear, making hydraulics (reduced-gravity shallow-water theory) rather than linear theory the simplest conceptual model to describe gap flow. Results from idealized topographical and flow conditions are presented, together with gap flows through a pass in the central Alpine Wipp Valley. For a given depth of the upstream reservoir, the gap controls the mass flux through it and marks the transition from a subcritical flow state upstream to a supercritical one downstream, which eventually adjusts to the downstream reservoir in a hydraulic jump. Three gap flow prototypes were found: a classical layer one with neutral stratification and a capping inversion and two with a continuous stratification, for which a special analytical self-similar hydraulic solution exists. In all three cases, a deepening wedge of nearly mixed and stagnant air forms on top of the gap flow plunging down from the pass. The descent causes a warming and (relative) drying of the air, making gap flows a special case of föhn. Topographical variations smaller than the gap scale cause additional hydraulic jumps, flow separation, vorticity banners, gravity waves, and interactions with cold pools. Turbulent friction cannot be neglected. The climatological frequency of gap flows depends on the establishment of two different reservoirs and reaches 20% for the Wipp

Titel:Gap flows: Results from the Mesoscale Alpine Programme
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iD
Mayr, Georg J.Univ. Innsbruck, Innsbruck, ANICHT SPEZIFIZIERT
Armi, LaurenceUniv. of California, San Diego, La Jolla, CA, USANICHT SPEZIFIZIERT
Gohm, AlexanderUniv. Innsbruck, InnsbruckNICHT SPEZIFIZIERT
Zängl, GüntherUniv. München, MünchenNICHT SPEZIFIZIERT
Durran, Dale R.Univ. of Washington, USANICHT SPEZIFIZIERT
Flamant, CyrilleInstitute Pierre Simon Laplace, FNICHT SPEZIFIZIERT
Gabersek, SasaUniv. of Ljubljana, SLONICHT SPEZIFIZIERT
Mobbs, StephenUniv. of Leeds, UKNICHT SPEZIFIZIERT
Ross, AndrewUniv. of Leeds, UKNICHT SPEZIFIZIERT
Datum:Februar 2007
Erschienen in:Quarterly Journal of the Royal Meteorological Society
Referierte Publikation:Ja
In Open Access:Nein
In ISI Web of Science:Ja
DOI :10.1002/qj.66
Seitenbereich:Seiten 881-895
Stichwörter:mountain, constriction, hydraulics, föhn
HGF - Forschungsbereich:Luftfahrt, Raumfahrt und Verkehr
HGF - Programm:Luftfahrt
HGF - Programmthema:L VU - Luftverkehr und Umwelt (alt)
DLR - Schwerpunkt:Luftfahrt
DLR - Forschungsgebiet:L VU - Luftverkehr und Umwelt
DLR - Teilgebiet (Projekt, Vorhaben):L - Luftverkehr und Wetter (alt)
Standort: Oberpfaffenhofen
Institute & Einrichtungen:Institut für Physik der Atmosphäre > Lidar
Hinterlegt von: Münster, Christiane
Hinterlegt am:13 Mär 2008
Letzte Änderung:20 Okt 2014 14:32

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