Analysis of second‐order moments in surface layer turbulence in an Alpine valley

Franceschi, Massimiliano de; Zardi, Dino; Tagliazucca, M.; Tampieri, F.

doi:10.1002/qj.506

Cited by 65 publications

(41 citation statements)

References 74 publications

(72 reference statements)

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“…We rejected data segments with the magnitude of the sensible heat flux |H | < 10 W m −2 as recommended by de Franceschi et al (2009) to exclude transition periods from the analysis, and thus to prevent indeterminate ratios such as σ θ /θ * l in the near-neutral regime.…”

Section: Datamentioning

confidence: 99%

“…Unfortunately, given our very sparse measurements of h, we could not test the performance of such scaling here. In an alpine valley, the largest turbulent eddies may also be constrained by the valley geometry (de Franceschi et al 2009).…”

Section: Dimensionless Standard Deviations Of Wind Velocity Componentsmentioning

confidence: 99%

“…The applicability of MOST has been extensively studied over a wide range of landscapes, from equatorial areas (Yusup et al 2008), to deserts (Tamagawa 1996), forests (Rannik 1998), wetlands (Marques et al 2008), alpine valley floors (de Franceschi et al 2009), heterogeneous surfaces (Andreas et al 1998), lakes (Drennan et al 1999), rugged hilly landscapes (Brutsaert and Kustas 1987), and urban areas (Nordbo et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…The formulation of the functions varies between studies, and with atmospheric stability, and an exhaustive review can be found in de Franceschi et al (2009). A widely accepted form for velocity fluctuations in the MOST framework is…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Similarity Scaling Over a Steep Alpine Slope

Nadeau

Pardyjak

Higgins

et al. 2012

Boundary-Layer Meteorol

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In this study, we investigate the validity of similarity scaling over a steep mountain slope (30-41 • ). The results are based on eddy-covariance data collected during the Slope Experiment near La Fouly (SELF-2010); a field campaign conducted in a narrow valley of the Swiss Alps during summer 2010. The turbulent fluxes of heat and momentum are found to vary significantly with height in the first few metres above the inclined surface. These variations exceed by an order of magnitude the well-accepted maximum 10 % required for the applicability of Monin-Obukhov similarity theory in the surface layer. This could be due to a surface layer that is too thin to be detected or to the presence of advective fluxes. It is shown that local scaling can be a useful tool in these cases when surface-layer theory breaks down. Under convective conditions and after removing the effects of self-correlation, the normalized standard deviations of slope-normal wind velocity, temperature and humidity scale relatively well with z/Λ, where z is the measurement height and Λ(z) the local Obukhov length. However, the horizontal velocity fluctuations are not correlated with z/Λ under all stability regimes. The non-dimensional gradients of wind velocity and temperature are also investigated. For those, the local scaling appears inappropriate, particularly at night when shallow drainage flows prevail and lead to negative wind-speed gradients close to the surface.

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Section: Datamentioning

confidence: 99%

Section: Dimensionless Standard Deviations Of Wind Velocity Componentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Similarity Scaling Over a Steep Alpine Slope

Nadeau

Pardyjak

Higgins

et al. 2012

Boundary-Layer Meteorol

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“…was equipped with an ultrasonic anemometer (de Franceschi et al, 2002). Eddy correlation techniques were applied to retrieve the vertical sensible heat flux, adopting an averaging period of 30 min (see de Franceschi and Zardi, 2003;de Franceschi et al, 2009). …”

Section: Surface Observationsmentioning

confidence: 99%

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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Residual kriging analysis of airborne measurements: application to the mapping of atmospheric boundary‐layer thermal structures in a mountain valley

Laiti

Zardi

Franceschi

et al. 2013

Atmospheric Science Letters

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Residual kriging (RK) is applied to data from measurements performed with an instrumented motorglider in an Alpine Valley, where a coupled lake and valley wind develops. Results provide an insight into a typical mean vertical structure of the valley boundary layer, displaying a rather shallow convective mixed layer, surmounted by a deep stable layer. Mapping with RK allows to detect spatial temperature anomalies associated with the local development of diurnal winds over each explored valley cross section. Local scale features, such as cross-valley thermal asymmetries, amenable to surface inhomogeneities and their effects on heat fluxes, are also identified.

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Analysis of second‐order moments in surface layer turbulence in an Alpine valley

Cited by 65 publications

References 74 publications

Similarity Scaling Over a Steep Alpine Slope

Similarity Scaling Over a Steep Alpine Slope

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

Residual kriging analysis of airborne measurements: application to the mapping of atmospheric boundary‐layer thermal structures in a mountain valley

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