Journal Article

The Critical Richardson Number and Limits of Applicability of Local Similarity Theory in the Stable Boundary Layer

Andreas, Edgar L, Grachev, Andrey A., Persson, P. Ola G., Fairall, Christopher W., Guest, Peter S.

2013

Overview

Measurements of atmospheric turbulence made over the Arctic pack ice during the Surface Heat Budget of the Arctic Ocean experiment (SHEBA) are used to determine the limits of applicability of Monin–Obukhov similarity theory (in the local scaling formulation) in the stable atmospheric boundary layer. Based on the spectral analysis of wind velocity and air temperature fluctuations, it is shown that, when both the gradient Richardson number, Ri , and the flux Richardson number, Rf , exceed a ‘critical value’ of about 0.20–0.25, the inertial subrange associated with the Richardson–Kolmogorov cascade dies out and vertical turbulent fluxes become small. Some small-scale turbulence survives even in this supercritical regime, but this is non-Kolmogorov turbulence, and it decays rapidly with further increasing stability. Similarity theory is based on the turbulent fluxes in the high-frequency part of the spectra that are associated with energy-containing/flux-carrying eddies. Spectral densities in this high-frequency band diminish as the Richardson–Kolmogorov energy cascade weakens; therefore, the applicability of local Monin–Obukhov similarity theory in stable conditions is limited by the inequalities Ri <  Ri cr and Rf <  Rf cr . However, it is found that Rf cr   =  0.20–0.25 is a primary threshold for applicability. Applying this prerequisite shows that the data follow classical Monin–Obukhov local z -less predictions after the irrelevant cases (turbulence without the Richardson–Kolmogorov cascade) have been filtered out.

• Publisher: Springer Netherlands,Springer,Springer Nature B.V
• Subject: Air temperature / Analysis / Atmospheric boundary layer / Atmospheric models / Atmospheric Protection/Air Quality Control/Air Pollution / Atmospheric Sciences / Atmospheric turbulence / Boundary layers / Cascades / Computational fluid dynamics / Convection, turbulence, diffusion. Boundary layer structure and dynamics / Earth and Environmental Science / Earth Sciences / Earth, ocean, space / Eddies / Exact sciences and technology / External geophysics / Heat budget / Marine / Meteorology / Non-Kolmogorov turbulence / Pack ice / Planetary boundary layer / Richardson number / Sea ice / Similarity theory / Spectra / Spectral analysis / Temperature / Turbulence / Turbulent flow / Wind speed