Środowiskowe Seminarium Fizyki Atmosfery

Gradient-based similarity functions, evaluated based on data generated by a large-eddy simulation model of the stably stratified boundary layer, are compared with analogous similarity functions, derived from field observations in the stable surface layer during the SHEBA experiment in the Arctic. The comparison is performed in terms of explicit and implicit local scaling systems for the temperature and momentum fluxes, standard deviations of the vertical velocity and of temperature, as well as dissipation rates for the turbulent kinetic energy and for the temperature variance. The explicit scaling employs the semi-empirical mixing length l as the length scale. Within the implicit scaling systems, the Dougherty–Ozmidov length scale L, the Ellison length L, and the vertical overturning scale Lw, are used as length scales. A satisfactory agreement of numerically simulated and experimentally assessed similarity functions is obtained in the range of larger values of the Richardson number, 0.02 < Ri < 0.2. The agreement is poorer near the underlying surface (i.e. for small values of Ri) due to the imperfect performance of the sub-grid parameterization within the large-eddy simulation model.