Author(s): Damien Bouffard; Ulrich Lemmin; Switzer Land
Linked Author(s): Ulrich Lemmin
Keywords: Turbulence measurements; Turbulent Kinetic Energy balance; Stratification; Lake of Geneva 2
Abstract: Vertical exchange processes are key to the comprehension of physical and biological dynamics in stratified lakes or oceans. Unfortunately the role of turbulent mixing in vertical exchanges is still poorly understood. This is mainly due to the difficulties to conduct field observations of turbulent mixing events, especially in the vicinity of the thermocline, of their relation to the forcing mechanisms and their development over time and space. Here we present a new experimental device to overcome most of these difficulties. Developed at the Environmental Hydraulic Laboratory (LHE-EPFL), this moored sensor platform has been designed to investigate finescale structure in time and in space. The platform is equipped with standard turbulence sensors for measuring shear velocity and temperature gradients as well as high precision thermistor probes and acoustic Doppler velocimeters. It is displaced in the vertical by a bottom-resting winch and is connected to the shore by a long cable which provides real time access to the data, allowing to control the winch and to optimise the measurement strategy. An intensive field campaign of over two months during which the system was permanently moored in the lake was carried out in autumn 2006 in the stratified Lake of Geneva and permitted us to validate the system‘s performance.
Year: 2007