High‐resolution wind speed measurements using actively heated fiber optics

Sayde, Chadi; Thomas, Christoph; Wagner, James; Selker, John S.

doi:10.1002/2015gl066729

Cited by 72 publications

(108 citation statements)

References 38 publications

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“…Over the past 10 years, Raman scattering DTS has been used in hydrology to monitor water temperatures over both long and short distances (Selker et al, 2006;Lowry et al, 2007;Petrides et al, 2011). Recently, the DTS technique has also been applied in the atmospheric and other geosciences: soil moisture (Sayde et al, 2010) and wind velocities (Sayde et al, 2015) were measured by means of heated fiber-optic cables, temperature profiles in the atmospheric boundary layer (Keller et al, 2011) were obtained, and turbulent structures in the surface layer could be resolved (Thomas et al, 2012). Strengths of the DTS technique include high spatial and temporal resolutions up to 0.13 m along the fiber at 1 s (Thomas et al, 2012;Hilgersom et al, 2016b), referencing all spatially distributed measurements to a single standard, and the universal applicability in air, water, and soil.…”

Section: Introductionmentioning

confidence: 99%

“…Similar to this idea, our study presents another novel and inexpensive support structure composed of a white, meshed reinforcing fabric and several transparent acrylic glass rings. Sayde et al (2015) proposed a detailed and quantitative energy balance model for an actively heated fiber cable in open air for the purpose of measuring the wind velocity orthogonal to the fiber-optic cable. This model included terms for individual shortwave and longwave radiation fluxes and convective heat transfer.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative analysis of the radiation error for aerial coiled-fiber-optic distributed temperature sensing deployments using reinforcing fabric as support structure

et al. 2017

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Abstract. In recent years, the spatial resolution of fiber-optic distributed temperature sensing (DTS) has been enhanced in various studies by helically coiling the fiber around a support structure. While solid polyvinyl chloride tubes are an appropriate support structure under water, they can produce considerable errors in aerial deployments due to the radiative heating or cooling. We used meshed reinforcing fabric as a novel support structure to measure high-resolution vertical temperature profiles with a height of several meters above a meadow and within and above a small lake. This study aimed at quantifying the radiation error for the coiled DTS system and the contribution caused by the novel support structure via heat conduction. A quantitative and comprehensive energy balance model is proposed and tested, which includes the shortwave radiative, longwave radiative, convective, and conductive heat transfers and allows for modeling fiber temperatures as well as quantifying the radiation error. The sensitivity of the energy balance model to the conduction error caused by the reinforcing fabric is discussed in terms of its albedo, emissivity, and thermal conductivity. Modeled radiation errors amounted to −1.0 and 1.3 K at 2 m height but ranged up to 2.8 K for very high incoming shortwave radiation (1000 J s −1 m −2 ) and very weak winds (0.1 m s −1 ). After correcting for the radiation error by means of the presented energy balance, the root mean square error between DTS and reference air temperatures from an aspirated resistance thermometer or an ultrasonic anemometer was 0.42 and 0.26 K above the meadow and the lake, respectively. Conduction between reinforcing fabric and fiber cable had a small effect on fiber temperatures (< 0.18 K). Only for locations where the plastic rings that supported the reinforcing fabric touched the fiber-optic cable were significant temperature artifacts of up to 2.5 K observed. Overall, the reinforcing fabric offers several advantages over conventional support structures published to date in the literature as it minimizes both radiation and conduction errors.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantitative analysis of the radiation error for aerial coiled-fiber-optic distributed temperature sensing deployments using reinforcing fabric as support structure

et al. 2017

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“…For one of the field measurements, we employed meteorological data as input for an energy balance model (Hilgersom et al, 2015) to compare the fibre heating for a cable surrounded by air and a cable attached to a PVC tube. Sayde et al (2015) has shown that energy balance models can function for modelling fibre temperatures.…”

Section: Introductionmentioning

confidence: 99%

Practical considerations for enhanced-resolution coil-wrapped distributed temperature sensing

Hilgersom

Emmerik

Solcerová

et al. 2016

Geosci. Instrum. Method. Data Syst.

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Abstract. Fibre optic distributed temperature sensing (DTS) is widely applied in Earth sciences. Many applications require a spatial resolution higher than that provided by the DTS instrument. Measurements at these higher resolutions can be achieved with a fibre optic cable helically wrapped on a cylinder. The effect of the probe construction, such as its material, shape, and diameter, on the performance has been poorly understood. In this article, we study data sets obtained from a laboratory experiment using different cable and construction diameters, and three field experiments using different construction characteristics. This study shows that the construction material, shape, diameter, and cable attachment method can have a significant influence on DTS temperature measurements. We present a qualitative and quantitative approximation of errors introduced through the choice of auxiliary construction, influence of solar radiation, coil diameter, and cable attachment method. Our results provide insight into factors that influence DTS measurements, and we present a number of solutions to minimize these errors. These practical considerations allow designers of future DTS measurement set-ups to improve their environmental temperature measurements.

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“…Through the universal functions of the Monin-Obukhov similarity theory estimates of the sensible heat flux can be made. This could be done either by measuring the wind speed over height (Stricker and Brutsaert, 1978) using DTS (Sayde et al, 2015) or by applying the flux-variance method (Katul et al, 1995). The Bowen ratio can then be used to calculate the latent heat flux.…”

Section: Conclusion and Recommendationsmentioning

confidence: 99%

“…soil heat flux (Bense et al, 2016), and wind speed (Sayde et al, 2015). First introduced by Euser et al (2014), DTS can also be used for measuring the Bowen ratio, to estimate the evaporation flux.…”

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confidence: 99%

Technical note: Using distributed temperature sensing for Bowen ratio evaporation measurements

Schilperoort

Coenders-Gerrits

Luxemburg

et al. 2018

Hydrol. Earth Syst. Sci.

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Abstract. Rapid improvements in the precision and spatial resolution of distributed temperature sensing (DTS) technology now allow its use in hydrological and atmospheric sciences. Introduced by Euser et al. (2014) is the use of DTS for measuring the Bowen ratio (BR-DTS), to estimate the sensible and latent heat flux. The Bowen ratio is derived from DTS-measured vertical profiles of the air temperature and wet-bulb temperature. However, in previous research the measured temperatures were not validated, and the cables were not shielded from solar radiation. Additionally, the BR-DTS method has not been tested above a forest before, where temperature gradients are small and energy storage in the air column becomes important.In this paper the accuracy of the wet-bulb and air temperature measurements of the DTS are verified, and the resulting Bowen ratio and heat fluxes are compared to eddy covariance data. The performance of BR-DTS was tested on a 46 m high tower in a mixed forest in the centre of the Netherlands in August 2016. The average tree height is 26 to 30 m, and the temperatures are measured below, in, and above the canopy. Using the vertical temperature profiles the storage of latent and sensible heat in the air column was calculated.We found a significant effect of solar radiation on the temperature measurements, leading to a deviation of up to 3 K. By installing screens, the error caused by sunlight is reduced to under 1 K. Wind speed seems to have a minimal effect on the measured wet-bulb temperature, both below and above the canopy. After a simple quality control, the Bowen ratio measured by DTS correlates well with eddy covariance (EC) estimates (r 2 = 0.59). The average energy balance closure between BR-DTS and EC is good, with a mean underestimation of 3.4 W m −2 by the BR-DTS method. However, during daytime the BR-DTS method overestimates the available energy, and during night-time the BR-DTS method estimates the available energy to be more negative. This difference could be related to the biomass heat storage, which is neglected in this study.The BR-DTS method overestimates the latent heat flux on average by 18.7 W m −2 , with RMSE = 90 W m −2 . The sensible heat flux is underestimated on average by 10.6 W m −2 , with RMSE = 76 W m −2 . Estimates of the BR-DTS can be improved once the uncertainties in the energy balance are reduced. However, applying, for example, Monin-Obukhov similarity theory could provide independent estimates for the sensible heat flux. This would make the determination of the highly uncertain and difficult to determine net available energy redundant.

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High‐resolution wind speed measurements using actively heated fiber optics

Cited by 72 publications

References 38 publications

Quantitative analysis of the radiation error for aerial coiled-fiber-optic distributed temperature sensing deployments using reinforcing fabric as support structure

Quantitative analysis of the radiation error for aerial coiled-fiber-optic distributed temperature sensing deployments using reinforcing fabric as support structure

Practical considerations for enhanced-resolution coil-wrapped distributed temperature sensing

Technical note: Using distributed temperature sensing for Bowen ratio evaporation measurements

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