Test measurements with an operational microstructure-turbulence profiler: Detection limit of dissipation rates

Abstract

The MST (Microstructure-Turbulence) Profiler is a newly developed operational microstructure measuring system, specially designed for marine and limnic turbulence measurements. The profiler can be used for sinking and uprising measurements and is equipped with a new type of current shear sensor. We have tested the MST Profiler in several field measuring campaigns in deep Alpine lakes. The investigations were focused on the internal vibration level of the profiler and its lower detection limit for dissipation rate estimates (pseudo dissipation). The upper detection limit was estimated based on the geometry of the shear sensor. The test measurements gave no indication of pronounced internal profiler vibrations interfering with dissipation measurements. The pseudo dissipation level (noise) of the profiler was found to be as low as 5 · 10 -12 W/kg under quiet conditions at sinking velocities below 0.4 m/s. At 0.8 m/s sinking velocity, a pseudo dissipation of 4 · 10 -11 W/kg was obtained. At rising measurements with additional sources of profiler vibrations due to influence of the cable the pseudo dissipation is about twice that for sinking measurements. For the upper detection limit which can be measured without correction for unresolved variance of the shear spectrum, a value of 10 -4 W/kg was estimated.

Diapycnal heat flux and mixed layer heat budget within the Atlantic Cold Tongue

“…The profilers were adjusted to descend at 0.5-0.6 m s −1 . Noise levels of turbulent dissipation rates from the microstructure profilers are better than 1 × 10 −9 W kg −1 for the MSS90L and better than 5 × 10 −10 W kg −1 for MSS90D (Prandke and Stips 1998;Schafstall et al 2010).…”

“…All profilers were equipped with two shear sensors (airfoil), a fast temperature sensor (FP07), an acceleration sensor, tilt sensors and standard CTD sensors. For a detailed description of the instruments the reader is referred to Prandke and Stips (1998). The profilers were adjusted to descend at 0.5-0.6 m s −1 .…”

Biological N2 Fixation in the Upwelling Region off NW Iberia: Magnitude, Relevance, and Players

“…Water samples were collected for the determination of inorganic nutrients, chlorophyll a, primary production, picoplankton composition, biological N 2 fixation, as well as for DNA extraction. In 7 out of the 10 surveys, measurements of dissipation rates of turbulent kinetic energy were conducted using a microstructure turbulence profiler (MSS, Prandke and Stips, 1998).…”

Upper pycnocline turbulence in the northern South China Sea

“…Microstructure measurements were conducted at 38 stations in the northern SCS during two cruises in the summer monsoon seasons of 2009 (July 25-August 13) and 2010 (May 17-21) using the MSS-60 profiler [18]. Twenty-four stations of the year 2009 cruise were mainly aligned along three cross-shelf sections marked in red in Figure 1 as E, A and S, respectively.…”