The METCRAX II Field Experiment: A Study of Downslope Windstorm-Type Flows in Arizona’s Meteor Crater

Lehner, Manuela; Whiteman, C. David; Hoch, Sebastian W.; Crosman, Erik T.; Jeglum, Matthew E.; Cherukuru, Nihanth W.; Calhoun, Ronald; Adler, Bianca; Kalthoff, Norbert; Rotunno, Richard; Horst, Thomas; Semmer, Steven R.; Brown, William O.; Oncley, Steven; Vogt, Roland; Grudzielanek, A. Martina; Čermák, Jan; Fonteyne, Nils J.; Bernhofer, Christian; Pitacco, Andrea; Klein, Petra M.

doi:10.1175/bams-d-14-00238.1

Cited by 45 publications

(49 citation statements)

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“…On the other hand, deep katabatic flows with jet maxima between 20 and 40 m above ground level (agl) develop regularly at the METCRAX II NEAR tower (cf. Lehner et al, ; Savage et al, ). Persistent shallow katabatic flows with a jet maximum at around 5 m agl are also found at MATERHORN ES4 and ES5 towers located at the top of a relatively shallow slope below a couloir (Grachev et al, ).…”

Section: Methodsmentioning

confidence: 99%

“…In this study we examine turbulence measurements from 12 flux towers located on surfaces of different complexity, ranging from flat to highly complex mountainous terrain and over different types of surface. These are part of well-known data sets and include the tower at Cabauw experimental site for atmospheric research (Cesar) of the Royal Netherlands Meteorological Institute (e.g., Beljaars & Bosveld, 1997), the Cooperative Atmosphere-Surface Exchange Study 1999 (CASES-99; Poulos et al, 2002), the Terrain-induced Rotor Experiment (T-Rex; Grubišič et al, 2008), the Mountain Terrain Atmospheric Modeling and Observations Fernando et al, 2015), the Second Meteor Crater Experiment (METCRAX II; Lehner et al, 2016), and the Innsbruck Box (i-Box; Rotach et al, 2017). A detailed description of the data sets is given in Table 1.…”

Section: Data Setsmentioning

confidence: 99%

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Scaling, Anisotropy, and Complexity in Near‐Surface Atmospheric Turbulence

2019

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The development of a unified similarity scaling has so far failed over complex surfaces, as scaling studies show large deviations from the empirical formulations developed over flat and horizontally homogeneous terrain as well as large deviations between the different complex terrain data sets. However, a recent study of turbulence anisotropy for flat and horizontally homogeneous terrain has shown that separating the data according to the limiting states of anisotropy (isotropic, two‐component axisymmetric and one‐component turbulence) improves near‐surface scaling. In this paper we explore whether this finding can be extended to turbulence over inclined and horizontally heterogeneous surfaces by examining near‐surface scaling for 12 different data sets obtained over terrain ranging from flat to mountainous. Although these data sets show large deviations in scaling when all anisotropy types are examined together, the separation according to the limiting states of anisotropy significantly improves the collapse of data onto common scaling relations, indicating the possibility of a unified framework for turbulence scaling. A measure of turbulence complexity is developed, and the causes for the breakdown of scaling and the physical mechanisms behind the turbulence complexity encountered over complex terrain are identified and shown to be related to the distance to the isotropic state, prevalence of directional shear with height in mountainous terrain, and the deviations from isotropy in the inertial subrange.

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Section: Methodsmentioning

confidence: 99%

Section: Data Setsmentioning

confidence: 99%

Scaling, Anisotropy, and Complexity in Near‐Surface Atmospheric Turbulence

2019

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“…While these research programmes addressed a broad range of scientific questions, a number of other campaigns targeted specific phenomena, generally in mountain areas with relatively limited geographical extent (ASCOT [26], BLLAST [27], COLPEX [28], COPS [29], CUPIDO [30], DOMEX [31], MATERHORN [32], METCRAX [33], METCRAX II [34], PAP [35], PCAPS [36], Pic 2005 [37], TRACT [38], T-REX [39], VERTIKATOR [40], VOTALP [41], and VTMX [42]). Although they did not focus primarily on exchange in the ABL over mountains, all of these experimental efforts indirectly led to significant progress in the understanding of the relevant processes.…”

Section: Introductionmentioning

confidence: 99%

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

et al. 2018

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Abstract:The exchange of heat, momentum, and mass in the atmosphere over mountainous terrain is controlled by synoptic-scale dynamics, thermally driven mesoscale circulations, and turbulence. This article reviews the key challenges relevant to the understanding of exchange processes in the mountain boundary layer and outlines possible research priorities for the future. The review describes the limitations of the experimental study of turbulent exchange over complex terrain, the impact of slope and valley breezes on the structure of the convective boundary layer, and the role of intermittent mixing and wave-turbulence interaction in the stable boundary layer. The interplay between exchange processes at different spatial scales is discussed in depth, emphasizing the role of elevated and ground-based stable layers in controlling multi-scale interactions in the atmosphere over and near mountains. Implications of the current understanding of exchange processes over mountains towards the improvement of numerical weather prediction and climate models are discussed, considering in particular the representation of surface boundary conditions, the parameterization of sub-grid-scale exchange, and the development of stochastic perturbation schemes.

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“…It is about 1.2 km in diameter, 170 m in depth, and is surrounded by a rim that extends 30-50 m above the surrounding plain, which rises slightly to the south-west with a slope angle of about 1 • . Two major field campaigns, the Meteor Crater Experiment (METCRAX; Whiteman et al 2008) and METCRAX II (Lehner et al 2016b), were performed to study various aspects of the crater meteorology. The focus of METCRAX II in October 2013 was on the flow past the crater basin.…”

Section: The Nocturnal Atmosphere In the Meteor Cratermentioning

confidence: 99%

Flow Separation in the Lee of a Crater Rim

Lehner

Whiteman

Hoch

et al. 2019

Boundary-Layer Meteorol

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The nearly circular Meteor Crater, Arizona, is located on an extensive, slightly sloping plain, above which a south-westerly katabatic flow forms during undisturbed, clear-sky nights. For the katabatic flow over the upstream crater rim, the resulting flow regime in the lee depends on the upstream wind speed. For a shallow katabatic flow with a wind-speed maximum of about 5 m s −1 or less at a height of about 20 m above the ground, the flow decelerates as it approaches the crater. Cold-air intrusions form, that is, cold air spills over the crater rim and runs down the inner southwest sidewall. For a deep katabatic flow with a wind-speed maximum located above the 50-m high measurement tower and comparatively higher wind speeds, the flow accelerates towards the crater. The flow separates in the immediate lee of the crater rim, forming a wake over the southwest crater sidewall. The wake can either be small, affecting only the upper part of the sidewall, or large, affecting the entire crater sidewall or even the crater floor. When flow separation occurs, the wake region over the crater sidewall is characterized by low wind speeds and potentially a return circulation near the surface. Particularly for large wakes, stability in the crater atmosphere is reduced and relatively high wind speeds occur at the crater floor, which is otherwise submerged in a strong surface-based inversion. Turbulent kinetic energy at the crater sidewall is typically higher during cold-air intrusions than is the case during flow separation, but high values can occur at the floor when a large wake forms.

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The METCRAX II Field Experiment: A Study of Downslope Windstorm-Type Flows in Arizona’s Meteor Crater

Cited by 45 publications

References 46 publications

Scaling, Anisotropy, and Complexity in Near‐Surface Atmospheric Turbulence

Scaling, Anisotropy, and Complexity in Near‐Surface Atmospheric Turbulence

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

Flow Separation in the Lee of a Crater Rim

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