Measuring heat balance residual at lake surface using Distributed Temperature Sensing

Abstract

This research presents a new method to verify the measurements of surface fluxes and the heat balance at a lake surface, by means of Distributed Temperature Sensing (DTS) measurements from 0.5 m above to 1.5 m below the surface. Using a polyvinyl chloride hyperboloid construction, a floating standalone measuring device was developed. Being an open construction, it is almost insensitive to direct radiation. With this construction, a spiral‐shaped fiberoptic cable setup was created that obtained temperature measurements with a vertical spatial resolution of 0.0002 m and a temporal resolution of 1 min. DTS measured the detailed variations in air and surface water temperature. The new method was tested in the deep Lake Kinneret (Israel) from 6 to 9 Oct 2011 and in the shallow Lake Binaba (Ghana) from 24 to 28 Oct 2011. With the developed method, it is possible to capture the heat storage change in the top water layer, and therefore verify the water surface heat balance on a time scale of several minutes. Furthermore, a comparison was made between the measured temperature profiles of the airwater interface in Lake Kinneret and Lake Binaba. It was shown that the usage of DTS measurements for the verification of surface energy balance was applicable for Lake Kinneret, but probably not suitable for the conditions in the shallow Lake Binaba. In the latter, heat storage changes near the lake surface were not only caused by surface energy fluxes, but by internal heat waves and currents that bring cooler water to the upper layer.