On Parameterization of Dissipative Processes in Turbulent Transport Models for Description of Thermohydrodynamics and Biogeochemistry of Stratified Inland Water Bodies

• Published in: Izvestiya. Atmospheric and oceanic physics Vol. 60; no. 3; pp. 286 - 296
• Main Authors: Gladskikh, D. S., Mortikov, E. V.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-06-2024
• Subjects: Climatology; Earth and Environmental Science; Earth Sciences; Geophysics/Geodesy; gas transfer; stable stratification; biogeochemical processes; turbulent Prandtl number; turbulence; numerical simulation; inland water body
• ISSN: 0001-4338; 1555-628X
• DOI: 10.1134/S0001433824700257

In this paper, we discuss parameterizations of turbulent mixing processes in models of inland water bodies (lakes and reservoirs) that allow one to sustain turbulent fluctuations in the presence of small velocity shears even in the case of highly stable stratification. The proposed parameterization of the turbulent Prandtl number takes into account the nongradient correction for the mass flux and depends on two parameters: the anisotropy parameter, which describes the differences in the vertical and horizontal scales of the density field correlations, and the maximum flux Richardson number. It is shown that the value of the maximum flux Richardson number and, as a consequence, the asymptotical increase in the turbulent Prandtl number under strong stability are associated with differences in the integral time scales determined by the dissipation rate of the kinetic or potential energy and the fluctuation intensities of the corresponding fields. This is consistent with the direct numerical simulation of shear-driven stably stratified turbulence. The anisotropy parameter specifies the transitional regime from neutral stratification to strong stability. Using the proposed parameterization, numerical experiments are carried out to reproduce the thermal and biochemical regime of inland water bodies (Kuivajärvi Lake and Rybinsk Reservoir). The results show that the distribution of biochemical concentrations and gas transfer processes are more sensitive to specifying the value of the maximum flux Richardson number.