Assessment of a vertical high-resolution distributed-temperature-sensing system in a shallow thermohaline environment

In shallow thermohaline-driven lakes it is im- portant to measure temperature on fine spatial and tempo- ral scales to detect stratification or different hydrodynamic regimes. Raman spectra distributed temperature sensing (DTS) is an approach available to provide high spatial and temporal temperature resolution. A vertical high-resolution DTS system was constructed to overcome the problems of typical methods used in the past, i.e., without disturbing the water column, and with resistance to corrosive environments. This paper describes a method to quantitatively assess ac- curacy, precision and other limitations of DTS systems to fully utilize the capacity of this technology, with a focus on vertical high-resolution to measure temperatures in shallow thermohaline environments. It also presents a new method to manually calibrate temperatures along the optical fiber achieving significant improved resolution. The vertical high- resolution DTS system is used to monitor the thermal be- havior of a salt-gradient solar pond, which is an engineered shallow thermohaline system that allows collection and stor- age of solar energy for a long period of time. The vertical high-resolution DTS system monitors the temperature pro- file each 1.1 cm vertically and in time averages as small as 10 s. Temperature resolution as low as 0.035 C is obtained when the data are collected at 5-min intervals.

[1]  A. Wüest,et al.  Response of Lake Kivu stratification to lava inflow and climate warming , 2004 .

[2]  T. Gogolla,et al.  Spontaneous Raman scattering in optical fibers with modulated probe light for distributed temperature Raman remote sensing , 1999 .

[3]  Raul H. Piedrahita,et al.  Modelling temperature variation and thermal stratification in shallow aquaculture ponds , 1991 .

[4]  Scott W. Tyler,et al.  Temperature evolution of an experimental salt-gradient solar pond , 2010 .

[5]  M. Ozkaymak,et al.  Performance evaluation of a small‐scale sodium carbonate salt gradient solar pond , 2006 .

[6]  E. Rubiola,et al.  On the measurement of frequency and of its sample variance with high-resolution counters , 2005, Proceedings of the 2005 IEEE International Frequency Control Symposium and Exposition, 2005..

[7]  T. Torgersen,et al.  Predicting the onset of thermal stratification in shallow inland waterbodies , 2009, Aquatic Sciences.

[8]  Andrew Swift,et al.  Advancements in Salinity Gradient Solar Pond Technology Based on Sixteen Years of Operational Experience , 2004 .

[9]  Alan D. Kersey,et al.  Optical Fiber Sensors for Permanent Downwell Monitoring Applications in the Oil and Gas Industry , 2000 .

[10]  Enrico Rubiola,et al.  On the measurement of frequency and of its sample variance with high-resolution counters , 2005 .

[11]  W. H. Stevenson,et al.  Miniature fiber‐optic refractometer for measurement of salinity in double‐diffusive thermohaline systems , 1985 .

[12]  Bronislovas Kaulakys,et al.  Modeling scaled processes and 1/fβnoise using nonlinear stochastic differential equations , 2009 .

[13]  Manoj Menon,et al.  Processes controlling the thermal regime of saltmarsh channel beds. , 2008, Environmental science & technology.

[14]  F. V. Brock,et al.  Minimizing Errors Associated with Multiplate Radiation Shields , 1999 .

[15]  John S. Selker,et al.  Environmental temperature sensing using Raman spectra DTS fiber‐optic methods , 2009 .

[16]  Luc Thévenaz,et al.  Distributed fiber‐optic temperature sensing for hydrologic systems , 2006 .

[17]  Alan J. Rogers,et al.  Distributed optical-fibre sensing , 1999 .

[18]  D. Anati,et al.  The post‐ 1979 thermohaline structure of the Dead Sea and the role of double‐diffusive mixing , 1991 .

[19]  Tobias Vogt,et al.  Estimation of seepage rates in a losing stream by means of fiber-optic high-resolution vertical temperature profiling , 2010 .

[20]  Bethany T. Neilson,et al.  Solar radiative heating of fiber‐optic cables used to monitor temperatures in water , 2010 .

[21]  Francisco Suárez,et al.  A theoretical study of a direct contact membrane distillation system coupled to a salt-gradient solar pond for terminal lakes reclamation. , 2010, Water research.

[22]  Cynthia Rosenzweig,et al.  Assessment of observed changes and responses in natural and managed systems , 2007 .

[23]  Jonathan D. Cryer,et al.  Time Series Analysis , 1986 .

[24]  Chad W. Higgins,et al.  Albedo effect on radiative errors in air temperature measurements , 2009 .

[25]  Changhuei Yang,et al.  Fundamental sensitivity limit imposed by dark 1/f noise in the low optical signal detection regime. , 2008, Optics express.

[26]  J. N. Ross,et al.  Distributed optical fibre Raman temperature sensor using a semiconductor light source and detector , 1985 .

[27]  Sait Eser Karlik,et al.  A distributed optical fiber sensor for temperature detection in power cables , 2006 .

[28]  M. G. Watson,et al.  Low-frequency divergent X-ray variability in the Seyfert galaxy NGC4051 , 1987, Nature.

[29]  T. Torgersen,et al.  A new water column profiler for shallow aquatic systems , 2005 .

[30]  John S. Selker,et al.  A distributed stream temperature model using high resolution temperature observations , 2007 .

[31]  Alan D. Kersey.  Optical fiber sensors for downwell monitoring applications in the oil and gas industry , 1999, International Conference on Optical Fibre Sensors.

[32]  P. Young,et al.  Time series analysis, forecasting and control , 1972, IEEE Transactions on Automatic Control.

[33]  David R. Cox,et al.  Time Series Analysis , 2012 .

[34]  James P. McNamara,et al.  Spatially distributed temperatures at the base of two mountain snowpacks measured with fiber-optic sensors , 2008 .

[35]  Scott W. Tyler,et al.  A fully coupled, transient double-diffusive convective model for salt-gradient solar ponds , 2010 .

[36]  K. N. Seetharamu,et al.  Convection Heat Transfer , 2005 .