The Alaiz Experiment: untangling multi-scale stratified flows over
complex terrain

Santos, Pedro; Mann, Jakob; Vasiljević, Nikola; Cantero, Elena; Rodrigo, Javier Sanz; Borbón, Fernando; Martínez‐Villagrasa, Daniel; Martí, Belén López; Cuxart, Joan

doi:10.5194/wes-2020-89

Cited by 3 publications

(4 citation statements)

References 37 publications

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“…The simulated surface winds over the Alaiz mountain range are southerly, as over most of the area covered by the innermost domain, but they are southeasterly and easterly on the Elorz valley. The Ebro valley forms an orographic funnel that produces two main flow patterns, with northwesterly winds (called El Cierzo) and southeasterly winds (Santos et al., 2020). The latter can be intensified when passing the gap between the Alaiz mountain range and the Tajonar Ridge.…”

Section: Resultsmentioning

confidence: 99%

“…Based on radial velocity retrievals from two scanning lidars mainly, Santos et al. (2020) illustrated an atmospheric hydraulic jump that started on a clear‐sky autumnal afternoon over the Alaiz mountain range and Elorz valley in the northeast of Spain. Apart from previous results on smaller spatial scale experiments where hydraulic jumps (Lehner et al., 2016) and lee‐wave activity (Palma et al., 2019) were observed and simulated, this is one of the first times in which a hydraulic jump is measured in high detail using scanning lidars.…”

Section: Introductionmentioning

confidence: 99%

“…At Alaiz, the conditions are very favorable for the development of atmospheric hydraulic jumps. First, winds (southerly) on the windward slope and on top of the Alaiz mountain range are often nearly perpendicular to the ridge line; ≈25% of the time surface winds are south‐southeast (Santos et al., 2020). Second, for southerly winds the mountain range has a gentle windward slope and a steep leeward slope.…”

Section: Introductionmentioning

confidence: 99%

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Lidar Observations and Numerical Simulations of an Atmospheric Hydraulic Jump and Mountain Waves

Peña

Santos

2021

JGR Atmospheres

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Hydraulic jumps and other related phenomena have been studied for many decades (Long, 1953; Lyra, 1943; Rayleigh, 1883), and readers are referred to the survey of Chanson (2009) for details on the progress of experiments conducted in controlled channels mainly. Although results from theoretical studies and controlled experiments have provided us with the basis for understanding the jump mechanisms in the atmosphere, studies, and particularly, observations of atmospheric hydraulic jumps are not as common. Clarke (1972) was perhaps the first one who attempted to combine large-scale observations with simulations to explain an atmospheric phenomenon, the "morning glory," which is a frequent squall that occurs near dawn on the southern coast of the Gulf of Carpentaria, Australia, quite recognizable due to its narrow cloud bands. He concluded that the morning glory is a propagating undular hydraulic jump formed in a katabatic flow. He also suggested some of the conditions that favor the occurrence of such phenomena, among others, shallow inversions, steep slopes, and topographic funneling. However, observational studies of atmospheric jumps can be tracked further back (Manley, 1939; Holmboe & Klieforth, 1957). More recently, the studies of Mobbs et al. (2005) and Gohm et al. (2008) showed the close connection between mountain waves, downslope winds, and jump events. Other recent observational and numerical studies have further detailed the conditions at which atmospheric hydraulic jumps occur (Juliano et al., 2017; Rotunno & Bryan, 2018), To understand how an atmospheric hydraulic jump develops, we can start by assuming, very simplistically, that the flow can be represented by a two-layer model, the lowest layer being the atmospheric boundary layer (ABL) and the upper layer the free atmosphere (Samuelson, 1992). In complex terrain, for example, mountainous regions, the depth of the ABL, h, can be of the order of the terrain elevation and the nature of the flow depends upon the Froude number (Fr),

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lidar Observations and Numerical Simulations of an Atmospheric Hydraulic Jump and Mountain Waves

Peña

Santos

2021

JGR Atmospheres

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“…Nonetheless, they can be used to ensure that the developed model does not deteriorate the results for any sites. (Fernando et al, 2019) and over Alaiz in 2011-12 (Santos et al, 2020). Elevation data for the two Mexican sites, Cuauhtémoc and Mérida, and the site in South Africa, Humansdorp, are obtained from the Shuttle Radar Topography Mission (JPL, 2013) at 90 m resolution.…”

Section: Elevation Datamentioning

confidence: 99%

Satellite-based estimation of roughness lengths and displacement heights for wind resource modelling

Floors¹,

Badger²,

Troen³

et al. 2021

Preprint

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Abstract. Wind turbines in northern Europe are frequently placed in forests, which sets new wind resource modelling requirements. Accurate mapping of the land surface can be challenging at forested sites due to sudden transitions between patches with very different aerodynamic properties, e.g. tall trees, clearings, and lakes. Tree growth and deforestation can lead to temporal changes of the forest. Global or pan-European land cover data sets fail to resolve these forest properties, aerial lidar campaigns are costly and infrequent, and hand-digitization is labour-intensive and subjective. Here, we investigate the potential of using satellite observations to characterise the land surface in connection with wind energy flow modelling using the Wind Atlas Analysis and Application Program (WAsP). Collocated maps of the land cover, tree height, and Leaf Area Index (LAI) have been generated based on observations from the Sentinel-1 and -2 missions combined with the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2). Three different forest canopy models are applied to convert these maps to roughness lengths and displacement heights. We introduce a modified model, which can process detailed land cover maps containing both roughness lengths and displacement heights. Extensive validation is carried out through cross-prediction analyses at ten well-instrumented sites in various landscapes. We demonstrate that using the novel satellite-based input maps leads to lower cross-prediction errors of the wind power density than land cover databases at a coarser spatial resolution. Differences in the cross-predictions resulting from the three different canopy models are minor. The satellite-based maps show cross-prediction errors close to those obtained from aerial lidar scans and hand-digitised maps. This demonstrates the value of using detailed satellite-based land cover maps for micro-scale flow modelling.

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Orographic Test Cases

2023

Handbook of Wind Resource Assessment

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The Alaiz Experiment: untangling multi-scale stratified flows over complex terrain

Cited by 3 publications

References 37 publications

Lidar Observations and Numerical Simulations of an Atmospheric Hydraulic Jump and Mountain Waves

Lidar Observations and Numerical Simulations of an Atmospheric Hydraulic Jump and Mountain Waves

Satellite-based estimation of roughness lengths and displacement heights for wind resource modelling

Orographic Test Cases

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