The NY-Ålesund TurbulencE Fiber Optic eXperiment (NYTEFOX): investigating the Arctic boundary layer, Svalbard

Zeller, Marie-Louise; Huss, Jannis-Michael; Pfister, Lena; Lapo, Karl; Littmann, Daniela; Schneider, Johann; Schulz, Alexander; Thomas, Christoph

doi:10.5194/essd-13-3439-2021

Cited by 7 publications

(4 citation statements)

References 52 publications

(62 reference statements)

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“…The simulated height of the model revealed only altitudes of 20-50 m [13], while the measurement campaign by Vihma et al [30] with tethered balloons reveals long jets at a mean height of h = 514 m, a mean velocity of v = 6.5 m s and wind direction of SE, which were caused by katabatic flows from the nearby glacier Brøggerbreen [30]. In the ABL experiment NYTEFOX by Zeller et al [47] a typical speed of katabatic winds was observed with up to v ≤ 5 m s in parallel with clear sky conditions and a weak synoptic wind. In these conditions small-scale effects dominate the local ABL.…”

Section: Discussionmentioning

confidence: 95%

The Nature of the Ny-Ålesund Wind Field Analysed by High-Resolution Windlidar Data

2022

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In this work we present windlidar data for the research village Ny-Ålesund located on Svalbard in the European Arctic (78.923°N, 11.928°E) from 2013 to 2021. The data have a resolution of 50 m and 10 min with an overlapping height of about 150 m. The maximum range depends on the meteorologic situation. Up to 1000 m altitude the data availability is better than 71%. We found that the highest wind speeds occur in November and December, the lowest ones in June and July, up to 500 m altitude the wind is channelled strongly in ESE to NW direction parallel to the fjord axis and the synoptic conditions above 1000 m altitude already dominate. While the fraction of windy days (v>10ms) varies significantly from month to month, there is no overall trend of the wind visible in our data set. We define gusts and jets by the requirement of wind maxima v>2ms above and below a wind maximum. In total, more than 24,000 of these events were identified (corresponding to 6% of the time), of which 223 lasted for at least 100 min (“Long Jets”). All of these events are fairly equally distributed over the months relatively to the available data. Further, gusts and jets follow different distributions (in terms of altitude or depths) and occur more frequently for synoptic flow from roughly a southerly direction. Jets do not show a clear correlation between occurrence and synoptic flow. Gusts and jets are not related to cloud cover. We conclude that the atmosphere from 400 m to 1000 m above Ny-Ålesund is dominated by a turbulent wind shear zone, which connects the micrometeorology in the atmospheric boundary layer (ABL) with the synoptic flow.

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Section: Discussionmentioning

confidence: 95%

The Nature of the Ny-Ålesund Wind Field Analysed by High-Resolution Windlidar Data

2022

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“…The SoPhaBs described here have an improved design compared to an earlier type described in Lapo et al [17] and Zeller et al [18], particularly with respect to the thermoelectric control, carrying case, and handling and routing of the fiber-optic cables.…”

Section: Methodsmentioning

confidence: 93%

Solid-Phase Reference Baths for Fiber-Optic Distributed Sensing

Thomas

Huss

Abdoli

et al. 2022

Sensors

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Observations from Raman backscatter-based Fiber-Optic Distributed Sensing (FODS) require reference sections of the fiber-optic cable sensor of known temperature to translate the primary measured intensities of Stokes and anti-Stokes photons to the secondary desired temperature signal, which also commonly forms the basis for other derived quantities. Here, we present the design and the results from laboratory and field evaluations of a novel Solid-Phase Bath (SoPhaB) using ultrafine copper instead of the traditional mechanically stirred liquid-phase water bath. This novel type is suitable for all FODS applications in geosciences and industry when high accuracy and precision are needed. The SoPhaB fully encloses the fiber-optic cable which is coiled around the inner core and surrounded by tightly interlocking parts with a total weight of 22 kg. The SoPhaB is thermoelectrically heated and/or cooled using Peltier elements to control the copper body temperature within ±0.04 K using commercially available electronic components. It features two built-in reference platinum wire thermometers which can be connected to the distributed temperature sensing instrument and/or external measurement and logging devices. The SoPhaB is enclosed in an insulated carrying case, which limits the heat loss to or gains from the outside environment and allows for mobile applications. For thermally stationary outside conditions the measured spatial temperature differences across SoPhaB parts touching the fiber-optic cable are <0.05 K even for stark contrasting temperatures of ΔT> 40 K between the SoPhaB’s setpoint and outside conditions. The uniform, stationary known temperature of the SoPhaB allows for substantially shorter sections of the fiber-optic cable sensors of less than <5 bins at spatial measurement resolution to achieve an even much reduced calibration bias and spatiotemporal uncertainty compared to traditional water baths. Field evaluations include deployments in contrasting environments including the Arctic polar night as well as peak summertime conditions to showcase the wide range of the SoPhaB’s applicability.

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“…This enables measurements of the small-scale and rapidly changing gradients and individual turbulent eddies. By installing the cable in different configurations such as coils (Sigmund et al 2017;Zeller et al 2021), or arrays (Thomas et al 2012), sharp temperature gradients near the surface can be measured. Here, we apply a harp-shaped DTS set-up to measure the temperature profile over and within the grass with 2 cm resolution.…”

Section: Alternative Approach: Surface Length Scale For Short Canopiesmentioning

confidence: 99%

Rethinking the Roughness Height: An Improved Description of Temperature Profiles over Short Vegetation

Boekee,

van der Linden,

ten Veldhuis

et al. 2024

Boundary-Layer Meteorol

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In this study, we present an extension to the Monin–Obukov similarity theory (MOST) for the roughness sublayer (RSL) over short vegetation. We test our theory using temperature measurements from fiber optic cables in an array-shaped set-up. This provides a high vertical measurement resolution that enables us to measure the sharp temperature gradients near the surface. It is well-known that MOST is invalid in the RSL as the flow is distorted by roughness elements. However, to derive the surface temperature, it is common practice to extrapolate the logarithmic profiles down to the surface through the RSL. Instead of logarithmic behaviour defined by MOST near the surface, our observations show near-linear temperature profiles. This log-to-linear transition is described over an aerodynamically smooth surface by the Van Driest equation in classical turbulence literature. Here we propose that the Van Driest equation can also be used to describe this transition over a rough surface, by replacing the viscous length scale with a surface length scale $$L_s$$ L s that represents the size of the smallest eddies near the grass structures. We show that $$L_s$$ L s scales with the geometry of the vegetation and that the model shows the potential to be scaled up to tall canopies. The adapted Van Driest model outperforms the roughness length concept in describing the temperature profiles near the surface and predicting the surface temperature.

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The NY-Ålesund TurbulencE Fiber Optic eXperiment (NYTEFOX): investigating the Arctic boundary layer, Svalbard

Cited by 7 publications

References 52 publications

The Nature of the Ny-Ålesund Wind Field Analysed by High-Resolution Windlidar Data

The Nature of the Ny-Ålesund Wind Field Analysed by High-Resolution Windlidar Data

Solid-Phase Reference Baths for Fiber-Optic Distributed Sensing

Rethinking the Roughness Height: An Improved Description of Temperature Profiles over Short Vegetation

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