What Is a Foehn?

Brinkmann, W. A. R.

doi:10.1002/j.1477-8696.1971.tb04200.x

Cited by 93 publications

(57 citation statements)

References 16 publications

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“…Therefore, colder temperatures and rather rainy weather was present during the second half of July. In the last week of July, northerly Foehn winds (warm dry air descending in the lee of a mountain range; Brinkmann, 1971) dominated the weather in southern Switzerland. Hence, the JFJ was frequently within clouds.…”

Section: Meteorological Conditions During Clace2011mentioning

confidence: 99%

Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)

et al. 2014

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Abstract. Aerosols influence the Earth's radiation budget directly through absorption and scattering of solar radiation in the atmosphere but also indirectly by modifying the properties of clouds. However, climate models still suffer from large uncertainties as a result of insufficient understanding of aerosol-cloud interactions. At the high altitude research station Jungfraujoch (JFJ; 3580 m a.s.l., Switzerland) cloud condensation nuclei (CCN) number concentrations at eight different supersaturations (SS) from 0.24 % to 1.18 % were measured using a CCN counter during Summer 2011. Simultaneously, in-situ aerosol activation properties of the prevailing ambient clouds were investigated by measuring the total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems. Combining all experimental data, a new method was developed to retrieve the so-called effective peak supersaturation SS peak , as a measure of the SS at which ambient clouds are formed. A 17-month CCN climatology was then used to retrieve the SS peak values also for four earlier summer campaigns (2000, 2002, 2004 and 2010) where no direct CCN data were available. The SS peak values varied between 0.01 % and 2.0 % during all campaigns. An overall median SS peak of 0.35 % and dry activation diameter of 87 nm was observed. It was found that the difference in topography between northwest and southeast plays an important role for the effective peak supersaturation in clouds formed in the vicinity of the JFJ, while differences in the number concentration of potential CCN only play a minor role. Results show that air masses coming from the southeast (with the slowly rising terrain of the Aletsch Glacier) generally experience lower SS peak values than air masses coming from the northwest (steep slope). The observed overall median values were 0.41 % and 0.22 % for northwest and southeast wind conditions, respectively, corresponding to literature values for cumulus clouds and shallowlayer clouds. These cloud types are consistent with weather observations routinely performed at the JFJ.

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Section: Meteorological Conditions During Clace2011mentioning

confidence: 99%

Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)

et al. 2014

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“…Föhn is associated with a decrease in cloudiness in the lee, is strong and gusty, and is often channelled along gaps and valleys cut into the main ridge (Brinkmann, 1971;Seibert, 1990). Föhn may cause damage due to severe storms (Brinkmann, 1974), snow melting (Hoinka, 1985), of the air masses (moist subtropical air mass for south föhn, polar air mass for north föhn).…”

Section: Some Highlights and Controversies From Alpine Föhn Studies Smentioning

confidence: 99%

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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“…Associated with this pressure field, a south-westerly synoptic flow gave birth to a föhn episode in the Rhine valley. The 'föhn nose' (Brinkmann 1971) is apparent in the mean sea level field over Italy at 1200 and 1800 UTC. The föhn episode appeared to weaken on 6 November at 0000 UTC when the 'föhn nose' disappeared ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Föohn/cold‐pool interactions in the Rhine valley during MAP IOP 15

Flamant

Drobinski

Furger

et al. 2006

Quart J Royal Meteoro Soc

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SUMMARYThe föhn/cold-pool interactions in the lower Alpine Rhine valley documented in the framework of the Intensive Observing Period (IOP) 15 of the Mesoscale Alpine Programme (MAP) on 5 November 1999 are analysed. The present study focuses on the water vapour mixing ratio measurements acquired with the airborne differential absorption lidar LEANDRE 2 which enabled detailed documentation of the along-valley structure of the cold pool. LEANDRE 2 and microbarograph measurements revealed the presence of Kelvin-Helmholtz waves (KHW) at the top of the cold pool. The characteristics of the waves were different in the region of the coldpool leading edge (the southernmost part of the cold pool) and in the vicinity of the Bodensee (Lake Constance), further to the north. Gravity waves were also observed above the cold pool in the in situ aircraft data acquired in the vicinity of the Bodensee. The gravity waves are suspected to be triggered by the KHW at the top of the cold pool. We also investigate the respective role of the three known processes likely to control the structure of the cold pool and its erosion along the Rhine valley, namely (i) convection within the cold pool, (ii) turbulent erosion at the top of the cold pool due to the presence of KHW, and (iii) dynamic displacement of the cold pool by föhn air. The former two processes are likely not to play a role in the erosion of the cold pool observed in the course of this IOP. Finally, the temporal evolution of the heat budget advection term in the lower Rhine valley was investigated using temperature profiles derived from balloon soundings acquired at two sites which were overpassed by the cold-pool edge in the course of its displacement northwards during the early afternoon as the result of the action of the föhn, and then southwards in the late afternoon as the föhn weakened and cold air from the Bodensee area was filling the lower Rhine Valley.

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What Is a Foehn?

Cited by 93 publications

References 16 publications

Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)

Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.)

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

Föohn/cold‐pool interactions in the Rhine valley during MAP IOP 15

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