Variations of thermohaline structure and turbulent mixing on the Black Sea shelf at the beginning of autumn cooling

Lozovatsky, Iossif; Dillon, Thomas M.; Erofeev, A.; Nabatov, Valeri N.

doi:10.1016/s0924-7963(99)00018-4

Cited by 11 publications

(6 citation statements)

References 41 publications

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“…In addition, γ o , which is equivalent to γ mf , was evaluated (table 1) using independent measurements of B and P, and the results are approximated in figure 7 as .1) for the nocturnal stably stratified atmospheric boundary layer is in good agreement with many previous estimates of γ for natural waters. In ocean mixing studies, γ = 0.2 is frequently used [4,14,54,[56][57][58][59][60][61][62][63]; however, higher (up to 0.4) and lower (approx. 0.1) values of γ have also been suggested (e.g.…”

Section: Dependence Of Mixing Reynolds Numbers R Mχ and R Mf On Rimentioning

confidence: 99%

Mixing efficiency in natural flows

Lozovatsky

Fernando

2013

Phil. Trans. R. Soc. A.

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It is argued that the mixing efficiency of naturally occurring stratified shear flows, γ = Rf /(1− Rf ), where Rf is the flux Richardson number, is dependent on at least two governing parameters: the gradient Richardson number Ri and the buoyancy Reynolds number Re b = ε / vN 2 . It is found that, in the range approximately 0.03< Ri <0.4, which spans 10 4 < Re b <10 6 , the mixing efficiency obtained via direct measurements of fluxes and property gradients in the stable atmospheric boundary layer and homogeneous/stationary balance equations of turbulent kinetic energy (TKE) is nominally similar to that evaluated using the scalar balance equations. Outside these Ri and Re b ranges, the commonly used flux-estimation methodology based on homogeneity and stationarity of TKE equations breaks down (e.g. buoyancy effects are unimportant, energy flux divergence is significant or flow is non-stationary). In a wide range, 0.002< Ri <1, the mixing efficiency increases with Ri , but decreases with Re b . When Ri is in the proximity of Ri cr ∼0.1–0.25, γ can be considered a constant γ ≈0.16–0.2. The results shed light on the wide variability of γ noted in previous studies.

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Section: Dependence Of Mixing Reynolds Numbers R Mχ and R Mf On Rimentioning

confidence: 99%

Mixing efficiency in natural flows

Lozovatsky

Fernando

2013

Phil. Trans. R. Soc. A.

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“…Accordingly, to accurately determine the turbulence fluxes in natural aquatic systems (Lozovatsky et al 1999), « also has to be obtained precisely. The value of « can be obtained from small-scale shear measurements (Gargett et al 1984;Gregg and Horne 2009), indirectly from microtemperature data (Jonas et al 2003;Sanchez and Roget 2007), or from both methods (Kocsis et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Small-Scale Spectrum of a Scalar Field in Water: The Batchelor and Kraichnan Models

Sanchez

Roget

Planella

et al. 2011

Journal of Physical Oceanography

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The theoretical models of Batchelor and Kraichnan, which account for the smallest scales of a scalar field passively advected by a turbulent fluid (Prandtl . 1), have been validated using shear and temperature profiles measured with a microstructure profiler in a lake. The value of the rate of dissipation of turbulent kinetic energy « has been computed by fitting the shear spectra to the Panchev and Kesich theoretical model and the one-dimensional spectra of the temperature gradient, once « is known, to the Batchelor and Kraichnan models and from it determining the value of the turbulent parameter q. The goodness of the fit between the spectra corresponding to these models and the measured data shows a very clear dependence on the degree of isotropy, which is estimated by the Cox number. The Kraichnan model adjusts better to the measured data than the Batchelor model, and the values of the turbulent parameter that better fit the experimental data are q B 5 4.4 6 0.8 and q K 5 7.9 6 2.5 for Batchelor and Kraichnan, respectively, when Cox $ 50. Once the turbulent parameter is fixed, a comparison of the value of « determined from fitting the thermal gradient spectra to the value obtained after fitting the shear spectra shows that the Kraichnan model gives a very good estimate of the dissipation, which the Batchelor model underestimates.

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“…This emphasizes the importance of other governing parameters in determining AG in addition to Reb, which should be addressed in future studies. The notion is supported by results of Lozovatsky et aL (1999) who showed that the Reb averaged over a large number of samples pertinent to the turbulent regions is a function of the averaged Richardson numbe.r, the approximate dependence being Reb ~ Ri-2/3.…”

Section: (8a)mentioning

confidence: 69%

“…The bottom depth along a 16 km cross-shelf transect varied from 17 to 30 m. A sharp narrow thermohalocline separated the upper and near-bottom mixed layers. Details of the measurements and the analysis of vertical structure of the dissipation rates and other turbulence parameters can be found in Lozovatsky et aL (1999) and Lozovatsky and Fernando (2002). In the latter paper, in addition to the upper (UBL) and bottom (BBL) quasi-homogeneous layers, the authors have identified several other mixing regions in the water column such as, QHP-quasi homogeneous patch-region with Nz< 10-4 S-2 AP-active patch-region with e > 1.25 × 10 -9 W kg-1; SDP-stratified dissipative patch-region with e >1.25 × 10 -9 W kg -1 but N2< 10 -4 s-2; MDP-microstructure displacement patch-regions with the rms.…”

Section: Mixing Activity In Shallow Waters (Bulgarian Shelf Of the Blmentioning

confidence: 99%

Mixing in shallow waters: Measurements, processing, and applications

Lozovatsky

Roget

Fernado

2005

J Ocean Univ. China

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Microstrueture profiling measurements taken on a shallow Black Sea shelf and in Lake Banyoles and Boadella reservoir (Both in Spain) are analyzed to investigate the influence of boundary-layer-induced turbulence of various sources on mixing in the water interior. The state of turbulence in shallow waters is examined and details of mierostructure data processing and error analysis are discussed. The dependence between averaged activity parameter AG and buoyancy Reynolds number Reb for the shelf turbulence indicates that for Reb < 1 the state of turbulence can be described by the fossil turbulence model, which postulates Ao --Re 3/2. For Re----b > 1, however, the influence of R-~eb on AG is weak, signifying that the buoyancy Reynolds number can no longer serve as the governing parameter for active turbulent mixing. The generation of turbulence by a one-minute long wind bursts (the Boadella reservoir) increases the averaged dissipation rate (e) of the surface mixed layer by more than 5 times (up to 3 × 10 -6 Wkg-l). The influence of the wind burlts was also traced below the thermocline, where turbulent patches with (¢) = (10 -7 -10 -6) Wkg -I were generated. It is shown that the geothermal convection in Lake Banyoles produces intermittent turbulent patches with characteristic dissipation rate (e) = (2 x 10-s _ 3 x 10-7) W kg -1, which influences the overall vertical mixing in the basin.

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Variations of thermohaline structure and turbulent mixing on the Black Sea shelf at the beginning of autumn cooling

Cited by 11 publications

References 41 publications

Mixing efficiency in natural flows

Mixing efficiency in natural flows

Small-Scale Spectrum of a Scalar Field in Water: The Batchelor and Kraichnan Models

Mixing in shallow waters: Measurements, processing, and applications

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