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  • Wiley  (3)
  • Elvidge, Andrew D.  (3)
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  • Wiley  (3)
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  • 1
    Online Resource
    Online Resource
    Foehn jets over the Larsen C Ice Shelf, Antarctica
    Wiley ; 2015
    In:  Quarterly Journal of the Royal Meteorological Society Vol. 141, No. 688 ( 2015-04), p. 698-713
    Details
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 141, No. 688 ( 2015-04), p. 698-713
    Abstract: Previously unknown foehn jets have been identified to the east of the Antarctic Peninsula ( AP ) above the Larsen C Ice Shelf. These jets have major implications for the east coast of the AP , a region of rapid climatic warming and where two large sections of ice shelf have collapsed in recent years. During three foehn events across the AP , leeside warming and drying is seen in new aircraft observations and simulated well by the Met Office Unified Model ( MetUM ) at ∼1.5 km grid spacing. In case A, weak southwesterly flow and an elevated upwind inversion characterise a highly nonlinear flow regime with upwind flow blocking. In case C strong northwesterly winds characterise a relatively linear case with little upwind flow blocking. Case B resides somewhere between the two in flow regime linearity. The foehn jets – apparent in aircraft observations where available and MetUM simulations of all three cases – are mesoscale features (up to 60 km in width) originating from the mouths of leeside inlets. Through back trajectory analysis they are identified as a type of gap flow. In cases A and B the jets are distinct, being strongly accelerated relative to the background flow, and confined to low levels above the Larsen C Ice Shelf. They resemble the ‘shallow foehn’ of the Alps. Case C resembles a case of ‘deep foehn’, with the jets less distinct. The foehn jets are considerably cooler and moister relative to adjacent regions of calmer foehn air. This is due to a dampened foehn effect in the jet regions: in case A the jets have lower upwind source regions, and in the more linear case C there is less diabatic warming and precipitation along jet trajectories due to the reduced orographic uplift across the mountain passes.
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    URL: Article
    DOI: 10.1002/qj.2015.141.issue-688
    DOI: 10.1002/qj.2382
    RVK:
    UA 1000
    RVK:
    UA 7650
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 3142-2
    detail.hit.zdb_id: 2089168-4
    SSG: 14
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Moving towards a wave‐resolved approach to forecasting mountain wave induced clear air turbulence
    Wiley ; 2017
    In:  Meteorological Applications Vol. 24, No. 3 ( 2017-07), p. 540-550
    Details
    In: Meteorological Applications, Wiley, Vol. 24, No. 3 ( 2017-07), p. 540-550
    Abstract: Mountain wave breaking in the lower stratosphere is one of the major causes of atmospheric turbulence encountered in commercial aviation, which in turn is the cause of most weather‐related aircraft incidents. In the case of clear air turbulence (CAT), there are no visual clues and pilots are reliant on operational forecasts and reports from other aircraft. Traditionally mountain waves have been sub‐grid‐scale in global numerical weather prediction (NWP) models, but recent developments in NWP mean that some forecast centres (e.g. the UK Met Office) are now producing operational global forecasts that resolve mountain wave activity explicitly, allowing predictions of mountain wave induced turbulence with greater accuracy and confidence than previously possible. Using a bespoke turbulent kinetic energy diagnostic, the Met Office Unified Model (MetUM) is shown to produce useful forecasts of mountain CAT during three case studies over Greenland, and to outperform the current operational Met Office CAT prediction product (the World Area Forecast Centre (WAFC) London gridded CAT product) in doing so. In a long term, 17‐month, verification, MetUM forecasts yield a turbulence prediction hit rate of 80% with an accompanying false alarm rate of under 40%. These skill scores are a considerable improvement on those reported for the mountain wave component of the WAFC product, although no direct comparison is available. The major implication of this work is that sophisticated global NWP models are now sufficiently advanced to provide skilful forecasts of mountain wave turbulence.
    Type of Medium: Online Resource
    ISSN: 1350-4827 , 1469-8080
    URL: Issue
    URL: Article
    DOI: 10.1002/met.2017.24.issue-3
    DOI: 10.1002/met.1656
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 1482937-X
    Location Call Number Limitation Availability
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  • 3
    Online Resource
    Online Resource
    Foehn warming distributions in nonlinear and linear flow regimes: a focus on the Antarctic Peninsula
    Wiley ; 2016
    In:  Quarterly Journal of the Royal Meteorological Society Vol. 142, No. 695 ( 2016-01), p. 618-631
    Details
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 142, No. 695 ( 2016-01), p. 618-631
    Abstract: The structure of lee‐side warming during foehn events is investigated as a function of cross‐barrier flow regime linearity. Two contrasting cases of westerly flow over the Antarctic Peninsula (AP) are considered – one highly nonlinear, the other relatively linear. Westerly flow impinging on the AP provides one of the best natural laboratories in the world for the study of foehn, owing to its maritime setting and the Larsen C Ice Shelf (LCIS) providing an expansive, homogeneous and smooth surface on its east side. Numerical simulations with the Met Office Unified Model (at 1.5 km grid size) and aircraft observations are utilized. In case A, relatively weak southwesterly cross‐Peninsula flow and an elevated upwind inversion dictate a highly nonlinear foehn event, with mountain wave breaking observed. The consequent strongly accelerated downslope flow leads to high‐amplitude warming and ice‐shelf melt in the immediate lee of the AP. However this foehn warming diminishes rapidly downwind due to upward ascent of the foehn flow via a hydraulic jump. In case C, strong northwesterly winds dictate a relatively linear flow regime. There is no hydraulic jump and strong foehn winds are able to flow at low levels across the entire ice shelf, mechanically mixing the near‐surface flow, preventing the development of a strong surface inversion and delivering large fluxes of sensible heat to the ice shelf. Consequently, in case C ice‐melt rates are considerably greater over the LCIS as a whole than in case A. Our results imply that although nonlinear foehn events cause intense warming in the immediate lee of mountains, linear foehn events will commonly cause more extensive lee‐side warming and, over an ice surface, higher melt rates. This has major implications for the AP, where recent east‐coast warming has led to the collapse of two ice shelves immediately north of the LCIS.
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    URL: Article
    DOI: 10.1002/qj.2016.142.issue-695
    DOI: 10.1002/qj.2489
    RVK:
    UA 1000
    RVK:
    UA 7650
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 3142-2
    detail.hit.zdb_id: 2089168-4
    SSG: 14
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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