Numerical simulation of meso-gamma scale features of föhn at ground level in the Rhine valley

Jaubert, Geneviève; Bougeault, Philippe; Berger, Heinz; Chimani, Barbara; Flamant, Cyrille; Häberli, Christian; Lothon, Marie; Nuret, Mathieu; Vogt, S.

doi:10.1256/qj.03.197

Cited by 11 publications

(29 citation statements)

References 32 publications

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“…Closely connected to the wave monitoring by the sodars was the operation of microbarographs, which made possible the determination of the relevant characteristics (direction of propagation, phase speed, and wavelength) of gravity waves on top of the cold pool by detecting the related pressure signal on the ground . Several aircraft flying over the Rhine Valley target area (French Merlin IV and ARAT Fokker-27, UK C-130, Swiss Metair Dimona, USA NCAR Electra and NOAA P-3) measured averaged mean and turbulent variables (wind speed and direction, vertical wind, temperature, pressure, humidity, turbulent kinetic energy, momentum and heat fluxes), providing information on gravity-wave activity in relation to cold-pool erosion (Gubser and Richner, 2001;Jaubert et al, 2005;Flamant et al, 2006). Finally, the cold-pool removal was also monitored by three continuously running cameras mounted at ∼1800 m amsl (above mean sea level) on Hoher Kasten.…”

Section: Observation Networkmentioning

confidence: 99%

“…This was vital for the validation of the models. This network also contributed to the derivation of better initial conditions for research and NWP models (Zängl et al, 2004a;Jaubert et al, 2005) and the mesoscale analyzes extensively used for föhn investigations in the Rhine Valley (Drobinski et al, 2003a;Chimani et al, 2006;Flamant et al, 2006).…”

Section: Observation Networkmentioning

confidence: 99%

“…The jet associated with flow splitting at the scale of the Alps and flowing along the western flank of the range may affect the altitude of the föhn jet in the Rhine Valley. It is capable of triggering cold-air intrusions from the north into the Rhine Valley (Jaubert et al, 2005), lifting the föhn flow passing over the Alpine range off the ground in the lower Rhine Valley. These intrusions are favoured when the strong flowaround jet is positioned close to the Rhine Valley outlet and is oriented orthogonally to it.…”

Section: Numerical Modellingmentioning

confidence: 99%

“…Of course, these cold-pool removal processes may also occur simultaneously. The interaction between the cold pool and the föhn in the Rhine Valley was best documented during IOPs 8 and 9 (21-22 October 1999; Gubser and Richner, 2001) and IOP 15 (5 and 6 November 1999; Vogt and Jaubert, 2004;Jaubert et al, 2005;Flamant et al, 2006).…”

Section: Föhn/cold-pool Interactionmentioning

confidence: 99%

“…An important contribution to this discrepancy might arise from cold-air advection from the Alpine foreland. Surface observations and numerical simulations (Zängl et al, 2004a;Beffrey et al, 2004a;Jaubert et al, 2005) frequently indicate a light northerly flow within the cold pool, particularly when the preceding weather evolution formed a significant cold-air pool in the Alpine foreland. The pressure gradient driving this inflow is most likely due to the fact that gravity-wave dynamics tends to form a local pressure minimum at the boundary between the föhn and the cold pool (Zängl et al 2004a).…”

Section: Föhn/cold-pool Interactionmentioning

confidence: 99%

See 4 more Smart Citations

Föhn in the Rhine Valley during MAP: A review of its multiscale dynamics in complex valley geometry

Drobinski¹,

Steinacker²,

Richner³

et al. 2007

Quart J Royal Meteoro Soc

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This paper summarizes the findings of seven years of research on föhn conducted within the project 'Föhn in the Rhine Valley during MAP' (FORM) of the Mesoscale Alpine Programme (MAP). It starts with a brief historical review of föhn research in the Alps, reaching back to the middle of the 19th century. Afterwards, it provides an overview of the experimental and numerical challenges identified before the MAP field experiment and summarizes the key findings made during MAP in observation, simulation and theory. We specifically address the role of the upstream and cross-Alpine flow structure on föhn at a local scale and the processes driving föhn propagation in the Rhine Valley. The crucial importance of interactions between the föhn and cold-air pools frequently filling the lower Rhine Valley is highlighted. In addition, the dynamics of a low-level flow splitting occurring at a valley bifurcation between the Rhine Valley and the Seez Valley are examined. The advances in numerical modelling and forecasting of föhn events in the Rhine Valley are also underlined. Finally, we discuss the main differences between föhn dynamics in the Rhine Valley area and in the Wipp/Inn Valley region and point out some open research questions needing further investigation.

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Section: Observation Networkmentioning

confidence: 99%

Section: Observation Networkmentioning

confidence: 99%

Section: Numerical Modellingmentioning

confidence: 99%

Section: Föhn/cold-pool Interactionmentioning

confidence: 99%

Section: Föhn/cold-pool Interactionmentioning

confidence: 99%

See 3 more Smart Citations

Föhn in the Rhine Valley during MAP: A review of its multiscale dynamics in complex valley geometry

Drobinski¹,

Steinacker²,

Richner³

et al. 2007

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

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Japan's south foehn on the Toyama Plain: Dynamical or thermodynamical mechanisms?

Kusaka

Nishi

Kakinuma

et al. 2021

Intl Journal of Climatology

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Japanese society has recently taken a greater interest in foehn warming because it has caused record-breaking high temperatures and sudden damage to rice crops. This is the first comprehensive climatological study focused on Japan's south foehn, which blows across the Toyama Plain in the Hokuriku region. Climatological analyses, including an objective selforganizing map and subjective analysis of 198 south foehn cases, revealed that $68.2% of the foehns occurred while an extratropical cyclone was passing through the Sea of Japan. Approximately 19.7% of the remaining foehns blew while an anticyclone covered Japan. Only 5.1% of all foehns occurred during a typhoon, but very high temperatures occurred when typhoons were approaching. Foehns were observed in all seasons but tended to blow more often in spring, when there are many migratory anticyclones and cyclones.Most of the foehns begin at night and end or pause during the day. This is due to the removal of the nocturnal stable layer and the development of a local daytime pressure gradient on the lee side. The dynamical mechanism provides the primary explanation for Japan's south foehn. Surprisingly, the foehns with precipitation on windward mountains slopes accounted for only $19.2% of all cases, with $40.0% being typhoon cases. Most of these are likely of multiple type; a pure thermodynamical type of foehn is a rare occurrence. Numerical simulations and back trajectory analyses for 76 selected foehn cases revealed that the majority of the air parcels originated from the south and passed straight over the Hida Highlands, between two mountain ranges, as a hybrid type of gap and foehn winds.

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Synoptic‐flow interaction with valley cold‐air pools and effects on cold‐air pool persistence: Influence of valley size and atmospheric stability

Sheridan

2019

Quart J Royal Meteoro Soc

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Idealized two‐dimensional simulations have been used to examine the dependence of valley cold‐air pool (CAP) behaviour, morphology and duration (persistence) on terrain scale. The simulations use terrain of constant aspect ratio but ranging from modest to Alpine scale, under midlatitude winter conditions with a finite background flow and incorporating a diurnal cycle. CAPs in smaller valleys are found to be more morphologically constrained, whereas larger valleys provide scope for more complex flow dynamics and more dramatic interplay of the external flow with the valley, including gravity wave breaking. Simulations of a valley within a plateau show that, as valley depth exceeds the depth‐scale of the nocturnal stable boundary layer, the CAP becomes increasingly confined and sheltered from the background flow (reduced mixing), becoming harder to remove by processes related to daytime insolation, and it can eventually become persistent (never removed). Both the surrounding terrain and gravity wave dynamics are found to play a part in the enhancement of sheltering. Therefore background atmospheric stability and wind are also crucial, summarized in a non‐dimensional valley depth parameter which largely determines CAP duration. More stable conditions, representative of (for instance) large‐scale subsidence or warm advection aloft, result in longer durations and a greater likelihood of persistence. Stronger nocturnal radiative cooling results in stronger CAPs, which are harder again to remove. Several mechanisms appear to act in concert to give rise to these behaviours and the dependence on non‐dimensional valley depth. Replacing the valley‐in‐plateau with a double hill enhances wave breaking, which complicates the relationship to non‐dimensional valley depth, reducing CAP duration significantly when subsidence or warm advection‐like effects are absent.

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Numerical simulation of meso-gamma scale features of föhn at ground level in the Rhine valley

Cited by 11 publications

References 32 publications

Föhn in the Rhine Valley during MAP: A review of its multiscale dynamics in complex valley geometry

Föhn in the Rhine Valley during MAP: A review of its multiscale dynamics in complex valley geometry

Japan's south foehn on the Toyama Plain: Dynamical or thermodynamical mechanisms?

Synoptic‐flow interaction with valley cold‐air pools and effects on cold‐air pool persistence: Influence of valley size and atmospheric stability

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