Evolution of superficial lake water temperature profile under diurnal radiative forcing

Abstract

[1] In lentic water bodies, such as lakes, the water temperature near the surface typically increases during the day, and decreases during the night as a consequence of the diurnal radiative forcing (solar and infrared radiation). These temperature variations penetrate vertically into the water, transported mainly by heat conduction enhanced by eddy diffusion, which may vary due to atmospheric conditions, surface wave breaking, and internal dynamics of the water body. These two processes can be described in terms of an effective thermal diffusivity, which can be experimentally estimated. However, the transparency of the water (depending on turbidity) also allows solar radiation to penetrate below the surface into the water body, where it is locally absorbed (either by the water or by the deployed sensors). This process makes the estimation of effective thermal diffusivity from experimental water temperature profiles more difficult. In this study, we analyze water temperature profiles in a lake with the aim of showing that assessment of the role played by radiative forcing is necessary to estimate the effective thermal diffusivity. To this end we investigate diurnal water temperature fluctuations with depth. We try to quantify the effect of locally absorbed radiation and assess the impact of atmospheric conditions (wind speed, net radiation) on the estimation of the thermal diffusivity. The whole analysis is based on the results of fiber optic distributed temperature sensing, which allows unprecedented high spatial resolution measurements ($4 mm) of the temperature profile in the water and near the water surface.

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

“…Selker et al, 2006;Vogt et al, 2010;Westhoff et al, 2007Westhoff et al, , 2011, lakes (e.g. Vercauteren et al, 2011;Van Emmerik et al, 2013), and in the air (e.g. Thomas et al, 2012;Euser et al, 2014;De Jong et al, 2015).…”

“…Various authors (e.g. Selker et al, 2006;Vogt et al, 2010; al., 2011; Vercauteren et al, 2011;Arnon et al, 2014) have increased the vertical spatial resolution of DTS measurements by wrapping fibre optic cable around a solid PVC tube, a technique sometimes called high-resolution DTS (HR-DTS), yielding spatial resolutions between 4 and 11 mm. The downside of this approach is that stress on the fibre or the characteristics of the supporting materials such as PVC (polyvinyl chloride) tubes (in this article: auxiliary constructions) might also influence the temperature measurements.…”

“…Vercauteren et al, 2011;Van Emmerik et al, 2013). However, recent papers discuss several errors in DTS temperature measurements caused by practical considerations of the measurement set-up.…”

Fiber optic distributed temperature sensing for the determination of air temperature

“…Applications vary from temperature profiling of the subsurface: borehole observations (Freifeld et al, 2008), soils (Ciocca et al, 2012;Jansen et al, 2011;Sayde et al, 2010;Steele-Dunne et al, 2010); water: estuaries (Henderson et al, 2009), surface/groundwater (Lowry et al, 2007;Mamer and Lowry, 2013), solar ponds , streams (Selker et al, 2006;Vogt et al, 2010;Westhoff et al, 2007Westhoff et al, , 2011 and lakes (Vercauteren et al, 2011;van Emmerik et al, 2013); rocks (Read et al, 2013), ice caves (Curtis and Kyle, 2011), forests (Krause et al, 2013) and infrastructure: dam surveillance (Dornstadter, 1998), sewers , electric transmission cables (Yilmaz and Karlik, 2006) and gas pipelines (Tanimola and Hill, 2009).…”

Evaporation suppression and energy balance of water reservoirs covered with self-assembling floating elements

“…The quantification of the temperature profile within the water body is the key to defining surface heat fluxes and thus radiative energy storage into the reservoir. For 10 simplicity, we employed a one-dimensional energy balance equation with subsurface radiation absorption and diffusive heat transfer including molecular and eddy thermal diffusivity to describe the vertical temperature profile in a reservoir according to (Dake and Harleman, 1969;Vercauteren et al, 2011): to the absorption of radiative flux within the water body that is a function of depth (light attenuation) and time (diurnal/seasonal variation of incoming radiation) (Dake and Harleman, 1969): …”