[A-OS16] Frontiers of Ocean Mixing Research

[AOS16-P05] Performance of turbulence observations using a deep float with microstructure sensors without vibrations from motor for buoyancy adjustment

*Shuo Zhai¹, Ichiro Yasuda¹, Yasutaka Goto², Ken Yamaki³ (1.Atmosphere and Ocean Research Institute, The University of Tokyo, 2.Japan Meteorological Agency, 3.Tsurumi-Seiki Co., Ltd.)

Keywords:turbulence, a deep float, vibration

A deep float enables us to quantify circulation of water and substances by observing turbulence in deep layer automatically. A DeepNINJA invented by Tsurumi-Seiki Co., Ltd. observed turbulence with a shear probe and a fast-response thermistor from October, 2018 to April, 2019. Performances of the probes are shown. The float was set to increase its buoyancy when its speed gets lower than 0.2m/s. The shear probe are clearly affected by vibration generated by the engine. Dissipation rates estimated by velocity shear and temperature are compared by selecting the locations where the engine didn’ t work to show if the fast-response thermistor probe is affected by the vibration. Dissipation rate estimated by temperature is calculated by obtaining Batchelor’s wavenumber which is calculated from Kraichnan’s theoretical spectrum. The correction τ₀W^-0.32(τ₀=32ms)(Gregg & Meager 1986) is shown to be necessary to have consistent dissipation rates under the condition where the speed was less than 0.2 m/s. It has been shown that a shear probe isn' t able to measure dissipation rate which is weaker than 10^-10 W/kg. The consistency between a deep float and a VMP6000 has suggested that a fast-response thermistor is able to measure dissipation rate as weak as 10^-11 W/kg. The difference between a shear probe and a fast-response thermistor probe has suggested that a fast-response thermistor probe is useful to observe turbulence in deep ocean.