Revisiting wind speed measurements using actively heated fiber optics: a wind tunnel study

Ramshorst, Justus van; Coenders-Gerrits, Miriam; Schilperoort, Bart; Wiel, B.J.H. van de; Izett, Jonathan G.; Selker, John S.; Higgins, C. W.; Savenije, Hubert; Giesen, Nick van de

doi:10.5194/amt-13-5423-2020

Cited by 15 publications

(13 citation statements)

References 40 publications

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“…4c and 5), this implies either overall low velocities or a change in wind direction due to the directional dependence of the measurement technique (see Sect. 3.1.2;Pfister et al, 2019;van Ramshorst et al, 2020). Overall, variability is higher in time than in space.…”

Section: Final Datamentioning

confidence: 94%

“…As DTS devices yield only relative temperature measurements, portions of the fiber-optic cables are guided through known and stabilized temperature environments, so-called reference calibration sections, to convert the raw Stokes/antistokes ratios into physically meaningful environmental temperatures (Hausner et al, 2011;Van De Giesen et al, 2012;des Tombe et al, 2020). Typically, liquid water baths are used as reference sections in which the fiber-optic cable is loosely coiled while stratification is prevented by mechanical mixing.…”

Section: Fods Reference Bathsmentioning

confidence: 99%

“…First, the raw data were filtered according to instrument flags and plausibility limits. Subsequently, unphysical turbulence data were removed using a despiking routine (Vickers and Mahrt, 1997). A three-dimensional rotation routine was applied aligning the flow for each averaging interval into the horizontal along-and cross-wind components and eliminating the mean vertical component potentially caused by a tilt in the ultrasonic anemometer, surface conditions, or semi-stationary eddies of timescales exceeding the perturbation timescale (Wilczak et al, 2001).…”

Section: Ultrasonic Anemometersmentioning

confidence: 99%

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

Zeller

Huss

Pfister

et al. 2021

Earth Syst. Sci. Data

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Abstract. The NY-Ålesund TurbulencE Fiber Optic eXperiment (NYTEFOX) was a field experiment at the Ny-Ålesund Arctic site (78.9∘ N, 11.9∘ E) and yielded a unique meteorological data set. These data describe the distribution of heat, airflows, and exchange in the Arctic boundary layer for a period of 14 d from 26 February to 10 March 2020. NYTEFOX is the first field experiment to investigate the heterogeneity of airflow and its transport of temperature, wind, and kinetic energy in the Arctic environment using the fiber-optic distributed sensing (FODS) technique for horizontal and vertical observations. FODS air temperature and wind speed were observed at a spatial resolution of 0.127 m and a temporal resolution of 9 s along a 700 m horizontal array at 1 m above ground level (a.g.l.) and along three 7 m vertical profiles. Ancillary data were collected from three sonic anemometers and an acoustic profiler (minisodar; sodar is an acronym for “sound detection and ranging”) yielding turbulent flow statistics and vertical profiles in the lowest 300 m a.g.l., respectively. The observations from this field campaign are publicly available on Zenodo (https://doi.org/10.5281/zenodo.4756836, Huss et al., 2021) and supplement the meteorological data set operationally collected by the Baseline Surface Radiation Network (BSRN) at Ny-Ålesund, Svalbard.

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Section: Final Datamentioning

confidence: 94%

Section: Fods Reference Bathsmentioning

confidence: 99%

Section: Ultrasonic Anemometersmentioning

confidence: 99%

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

Zeller

Huss

Pfister

et al. 2021

Earth Syst. Sci. Data

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“…For the observation of wind speeds through FODS, an active approach is used and the fiber is utilized as a spatially resolved hotwire anemometer (van Ramshorst et al 2020;Sayde et al 2015). With this approach, temperature and wind speed observations can be obtained at temporal resolutions down to seconds and on spatial scales from tens of centimeters up to kilometers (Pfister et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Distributed sensing of wind direction using fiber-optic cables

Freundorfer

Lapo

Schneider

et al. 2021

Journal of Atmospheric and Oceanic Technology

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In the atmospheric boundary layer, phenomena exist with challenging properties such as spatial heterogeneity, particularly during stable weak wind situations. Studying spatially heterogeneous features requires spatially distributed measurements on fine spatial and temporal scales. Fiber-Optic Distributed Sensing (FODS) can provide spatially distributed measurements, simultaneously offering a spatial resolution on the order of decimeters and a temporal resolution on the order of seconds. While FODS has already been deployed to study various variables, FODS wind direction sensing has only been demonstrated in idealized wind tunnel experiments. We present the first distributed observations of FODS wind directions from field data. The wind direction sensing is accomplished by using pairs of actively heated fiber optic cables with cone-shaped microstructures attached to them. Here we present three different methods of calculating wind directions from the FODS measurements, two based on using combined wind speed and direction information and one deriving wind direction independently from FODS wind speed. For each approach, the effective temporal and spatial resolution is quantified using spectral coherence. With each method of calculating wind directions, temporal resolutions on the order of tens of seconds can be achieved. The accuracy of FODS wind directions was evaluated against a sonic anemometer, showing deviations of less than 15° most of the time. The applicability of FODS for wind direction measurements in different environmental conditions is tested by analysing the dependence of FODS wind direction accuracy and observable scales on environmental factors. Finally, we demonstrate the potential of this technique by presenting a period that displays spatial and temporal structures in the wind direction.

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“…Measuring atmospheric fluxes over complex ecosystems such as forests has always been problematic due to the height of the roughness elements, which typically extend several tens of meters (Wilson, 2002;Barr et al, 1994). The large roughness layer above a tall canopy also makes it difficult to apply many theories of wall flows as well as to apply and validate traditional similarity theory (Katul et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Decoupling of a Douglas fir canopy: a look into the subcanopy with continuous vertical temperature profiles

et al. 2020

Self Cite

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Abstract. Complex ecosystems such as forests make accurately measuring atmospheric energy and matter fluxes difficult. One of the issues that can arise is that parts of the canopy and overlying atmosphere can be turbulently decoupled from each other, meaning that the vertical exchange of energy and matter is reduced or hampered. This complicates flux measurements performed above the canopy. Wind above the canopy will induce vertical exchange. However, stable thermal stratification, when lower parts of the canopy are colder, will hamper vertical exchange. To study the effect of thermal stratification on decoupling, we analyze high-resolution (0.3 m) vertical temperature profiles measured in a Douglas fir stand in the Netherlands using distributed temperature sensing (DTS). The forest has an open understory (0–20 m) and a dense overstory (20–34 m). The understory was often colder than the atmosphere above (80 % of the time during the night, >99 % during the day). Based on the aerodynamic Richardson number the canopy was regularly decoupled from the atmosphere (50 % of the time at night). In particular, decoupling could occur when both u*<0.4 m s−1 and the canopy was able to cool down through radiative cooling. With these conditions the understory could become strongly stably stratified at night. At higher values of the friction velocity the canopy was always well mixed. While the understory was nearly always stably stratified, convection just above the forest floor was common. However, this convection was limited in its vertical extent, not rising higher than 5 m at night and 15 m during the day. This points towards the understory layer acting as a kind of mechanical “blocking layer” between the forest floor and overstory. With the DTS temperature profiles we were able to study decoupling and stratification of the canopy in more detail and study processes which otherwise might be missed. These types of measurements can aid in describing the canopy–atmosphere interaction at forest sites and help detect and understand the general drivers of decoupling in forests.

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Revisiting wind speed measurements using actively heated fiber optics: a wind tunnel study

Cited by 15 publications

References 40 publications

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

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

Distributed sensing of wind direction using fiber-optic cables

Decoupling of a Douglas fir canopy: a look into the subcanopy with continuous vertical temperature profiles

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