Turbulence in theEastChinaSea:The summertime stratification

Abstract

A series of 134 microstructure profiles were taken in the central East China Sea from a drifting ship, covering more than 12 miles over the sloping bottom. The water depth z varied in the range 52-62 m; the tidal elevation of semidiurnal component was 61 m. Prior to the onset of 25 h drift, a hydrographic section consisting of 9 stations, 15 miles apart, was taken in the area. A shallow mixed surface layer (SL) underlain by a diurnal pycnocline (z < 13 m), a sharp thermohalocline (13 < z < 30 m), and about 20 m tall bottom boundary layer (BBL) were the main features of summertime stratification. The splitting of upper pycnocline by a warmer, saltier intrusion led to the generation of turbulent patches at the lower, but not at the upper, density interface of this water body, suggesting asymmetry of mixing across the intrusion. In a limited range of the normalized squared buoyancy frequency, 2 < N 2 =N 2 0 < 6:3, the turbulent kinetic energy dissipation rate e decreased sharply as e=e m 5 N 2 =N

Probability Distribution of Turbulent Kinetic Energy Dissipation Rate in Ocean: Observations and Approximations

“…Three commercially manufactured microstructure profilers that are commonly employed by the oceanographic community were used during the field campaigns. In the ECS (Liu et al, ; Lozovatsky et al, ; Lozovatsky, Jinadasa, et al, ; Lozovatsky, Lee, et al, ), we operated the MSS‐60 profiler (Prandke & Stips, ) and TurboMAP (Wolk et al, ), while in BoB/SL (Jinadasa et al, ; Wijesekera et al, ) and in GS (Lozovatsky et al, ), the measurements were taken by VMP‐500 (http://rocklandscientific.com/products/profilers/vmp-500/). In shallow waters (ECS) the measurements were collected in the depth range between the sea surface and 1–3 m above the sea floor; and in deep waters (BoB/SL and GS) the profilers descended to ∼130–150 m, being limited by the length of a tethered cable and weather conditions.…”

“… Bathymetry and main patterns of circulation in the East China Sea and Yellow Sea based on Zhang et al () and Lie and Cho (): TWC, Tsushima Warm Current; TAWC, Taiwan Warm Current; YSCC, Yellow Sea Coastal Current; YSWC, Yellow Sea Warm Current; CWC, Cheju Warm Current; ZMCC, Zhe‐Min Coastal Current. Measurements at stations S1 and S2 (Liu et al, ) and at CDW (Lozovatsky et al, ) were taken in 2006 using an MSS‐60 profiler; measurements at IK site (Lozovatsky, Jinadasa, et al, ; Lozovatsky, Lee, et al, ) were conducted in 2005 and 2006 using a TurboMAP profiler.…”

“…As has already been mentioned, the probability distributions of were found to be close to lognormal in boundary layers or large well‐mixed layers in the pycnocline, where the basic limitation, , of Gurvich and Yaglom () is met (e.g., Baker & Gibson, ; Moum et al, ; Wijesekera et al, ; Yamazaki & Lueck, ). However, it has recently been shown (Lozovatsky, Jinadasa, et al, ; Lozovatsky, Lee, et al, ) that the probability distribution of the logarithm of the dissipation rate ( ∼ 1.4 m) in strongly stratified pycnocline can follow the generalized extreme value distribution (Kotz & Nadarajah, ) given the rare, random generation of energetic turbulence events that form patches of high dissipation rate, while most of the background turbulence is confined to weakly dissipative regions that are at final stages of turbulence decay. Random patches of intense turbulence may affect tails of the dissipation rate probability distribution (Cuypers et al, ; Rousseau et al, ), making them heavier than the exponential bounds.…”

Ocean Turbulence and Mixing Around Sri Lanka and in Adjacent Waters of the Northern Bay of Bengal

“…Both VMPs carried two airfoil probes (to estimate the turbulent kinetic energy [TKE] dissipation rate ε), a three-component accelerometer, a pressure sensor (to calculate depth), and accurate temperature-conductivity sensors to obtain precise estimates of temperature, salinity, and potential density. The data processing followed the methodology of Roget et al (2006); additional information can be found in Liu et al (2009) and Lozovatsky et al (2015). Data above 5-10 m have been discarded due to the potential for ship-wake contamination.…”

Probability Distribution of Turbulent Kinetic Energy Dissipation Rate in Stratified Turbulence: Microstructure Measurements in the Southern California Bight

“…The probability distributions of dissipation field in a specific region can be influenced by larger‐scale dynamical processes that depend on energy sources and ambient stratification. Although non‐lognormality of in the stratified ocean has been demonstrated years ago (e.g., Baker & Gibson, ; Lozovatsky et al, ; Moum & Rippeth, ; Yamazaki & Lueck, ), no alternative statistical model has been proposed until Lozovatsky, Fernando, et al () reported the success of Burr XII distribution (e.g., Burr, ) to model the probability distribution of in the upper ocean pycnocline. This notion was supported by its application to various regions, including the East China Sea, Northern Indian Ocean, and Gulf Stream.…”