Diurnal Mountain Wind Systems

Zardi, Dino; Whiteman, C. David

doi:10.1007/978-94-007-4098-3_2

Cited by 195 publications

(194 citation statements)

References 377 publications

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“…Schmidli and Rotunno, 2010;Serafin and Zardi, 2010a, 2010bSchmidli, 2013). As a matter of fact, the daytime heating excess, which is typically found between the air within a mountain valley and over an adjacent plain and is responsible for driving up-valley winds (Zardi and Whiteman, 2013), is observed throughout the whole depth explored by the flights when the study area is compared with the Po Plain. It is found to be of the order of 0.5-1.5 K (see Sect.…”

Section: The Abl Structure In the Sarca And Lakes Valleysmentioning

confidence: 96%

Analysis of the diurnal development of a lake-valley circulation in the Alps based on airborne and surface measurements

et al. 2014

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Abstract. This study investigates the thermal structures of the atmospheric boundary layer (ABL) and the near-surface wind field associated with a lake-valley circulation in the south-eastern Italian Alps -the so-called Ora del Garda. Two flights of an equipped motorglider allowed for the exploration of the diurnal evolution of this circulation, from the onset, on Lake Garda's shoreline, throughout its development along the Sarca Valley and Lakes Valley (Valle dei Laghi), to the outflow into the Adige Valley. At the same time, surface observations, both from a targeted field campaign and from routinely operated weather stations, supported the analysis of the development of the Ora del Garda at the valley floor.In particular, in the valleys typical ABL vertical structures, characterized by rather shallow convective mixed layers (∼ 500 m) and (deeper) weakly stable layers above, up to the lateral crest height, are identified in the late morning. In contrast, close to the lake the ABL is stably stratified down to very low heights, as a consequence of the intense advection of colder air associated with the Ora del Garda flow (up to 6 m s −1 ). The combined analysis of surface and airborne observations (remapped over 3-D high-resolution grids) suggests that the lake-breeze front propagating up-valley from the shoreline in the late morning penetrates slightly later at the eastern end of the valley inlet (delay: ∼ 1 h), probably due to the asymmetric radiative forcing caused by the N-S valley orientation. On the other hand, in the early afternoon the Ora del Garda overflows through an elevated gap, producing an anomalous, strong cross-valley wind (5 m s −1 ) at the Adige Valley floor north of Trento, which overwhelms the local upvalley wind. This feature is associated with a strong deepening of the local mixed layer (from 400 to 1300 m). The potential temperature 3-D field suggests that the intense turbulent mixing may be attributed to the development of a downslope wind across the gap, followed by a hydraulic jump downstream.

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Section: The Abl Structure In the Sarca And Lakes Valleysmentioning

confidence: 96%

Analysis of the diurnal development of a lake-valley circulation in the Alps based on airborne and surface measurements

et al. 2014

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“…The diurnally reversing mountain-plain wind system occurs under fair weather conditions due to the formation of a nocturnal thermal high and a daytime thermal low over the Alps that can be attributed to the energy exchanges at the elevated Alpine terrain surfaces (Hafner et al, 1987;Sturman and Wanner, 2001;Zardi and Whiteman, 2013). Due to its spatial extension the mountain-plain wind system reveals considerable inertia.…”

Section: Introductionmentioning

confidence: 99%

“…Examples are the Rocky Mountains (Zardi and Whiteman, 2013), Central Japan (Kurita et al, 1990;Kuwagata et al, 1990), and the Southern Alps of New Zealand (Sturman and Wanner, 2001). The regional scale mountain-plain wind systems in these areas have been studied to investigate the transport of air pollutants, boundary layer growth, and thunderstorm development (Kurita et al, 1990;Kuwagata et al, 1990;Lugauer and Winkler, 2005).…”

Section: Introductionmentioning

confidence: 99%

Identification and Climatology of Alpine Pumping from a Regional Climate Simulation

et al. 2016

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The thermally driven circulation between the European Alps and the Alpine foreland-named Alpine pumping-occurs regularly under clear and calm weather conditions. While previous studies focused on the impact of Alpine pumping on moist convection and transport of air pollutants, this study was motivated by its ventilation effect for Munich, located about 50 km north of the Alps in undulating and only slightly inclined terrain, where local thermal circulations are weak. Hourly data from a reanalysis driven regional climate simulation with COSMO-CLM model for the period 1989-2008 were analyzed to identify days with Alpine pumping and to determine the mean diurnal characteristics of this regional thermal circulation. Four literature derived combinations of meteorological criteria were tested to identify days favorable for Alpine pumping from COSMO-CLM results. The first criterion selects days with a daily sum of solar radiation ≥20 MJ/m 2 and has been used in an earlier observational study. On average 60 day/year are fulfilling the criterion in the model simulation, which compares well to the 67 day/year determined from observations. The other three criteria combinations consider a maximum wind velocity at 850 hPa, a maximum daily precipitation sum, and/or a maximum mean cloud cover. The mean annual number of selected days is lower for these criteria combinations and ranges between 20 and 52. Diurnal wind reversals occur on 77-81% of the selected days, depending on the criteria combination. The daily solar radiation sum of 20 MJ/m 2 is only exceeded during April to September, while days satisfying the criteria combinations without the radiation threshold occur all year round. In agreement with observations, the simulated regional thermally driven wind field extends up to ∼100 km north of the Alps with average near-surface wind speeds of 0.5-1.5 m/s in the Munich area. With increasing distance from the Alps, the diurnal cycle of Alpine pumping is delayed by up to 3 h. The simulated mean depth of the daytime inflow layer ranges between 500 and 1500 m, whereas the depth of the nocturnal outflow layer typically reaches up to a few hundred meters.

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“…The following are typical characteristics of gap winds: an along-gap wind that is stronger than the diurnal winds, lack of a jet-like profile, lack of flow reversal at the usual morning transition time, and a favorable along-gap pressure gradient (e.g., [1]). All of these characteristics are observed during the gap winds in the study area.…”

Section: Introductionmentioning

confidence: 99%

“…The affected passages vary widely in scale and geometry and include gaps (terrain openings connecting mountain ranges), canyons or channels, passes, and straits. Flow induced by an along-passage pressure gradient is referred to as pressure-driven channeling (e.g., [1]). The cause of the pressure gradient and the resulting flow signature can vary from site-to-site according to the local terrain geometry and atmospheric conditions; however, the general mechanism and flow characteristics are similar among sites.…”

Section: Introductionmentioning

confidence: 99%

Observations and Predictability of Gap Winds in the Salmon River Canyon of Central Idaho, USA

et al. 2018

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This work investigates gap winds in a steep, deep river canyon prone to wildland fire. The driving mechanisms and the potential for forecasting the gap winds are investigated. The onset and strength of the gap winds are found to be correlated to the formation of an along-gap pressure gradient linked to periodic development of a thermal trough in the Pacific Northwest, USA. Numerical simulations are performed using a reanalysis dataset to investigate the ability of numerical weather prediction (NWP) to simulate the observed gap wind events, including the timing and flow characteristics within the canyon. The effects of model horizontal grid spacing and terrain representation are considered. The reanalysis simulations suggest that horizontal grid spacings used in operational NWP could be sufficient for simulating the gap flow events given the regional-scale depression in which the Salmon River Canyon is situated. The strength of the events, however, is under-predicted due, at least in part, to terrain smoothing in the model. Routine NWP, however, is found to have mixed results in terms of forecasting the gap wind events, primarily due to problems in simulating the regional sea level pressure system correctly.

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Diurnal Mountain Wind Systems

Cited by 195 publications

References 377 publications

Analysis of the diurnal development of a lake-valley circulation in the Alps based on airborne and surface measurements

Analysis of the diurnal development of a lake-valley circulation in the Alps based on airborne and surface measurements

Identification and Climatology of Alpine Pumping from a Regional Climate Simulation

Observations and Predictability of Gap Winds in the Salmon River Canyon of Central Idaho, USA

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