High resolution DNS of jet stream generated tropopausal turbulence

[1] Tropopausal turbulence (TT), generated by jet streams, is examined, for different nonhomogeneous basic state forcing profiles, through high resolution three-dimensional (3D) direct numerical simulations (DNS). Turbulent core regions, on either side of the jet, are characterized by a dramatic decrease in Brunt-Vaisala frequency (N), minima in gradient Richardson number (Rig) and shear length scales, and maxima in buoyancy Reynolds number and buoyancy length scales. The edges of turbulent mixing layers are marked by N2-bulges, which provides an alternate mechanism for multiple tropopauses. While temperature variance peaks in the vicinity of these N2-bulges, velocity variances peak within the turbulent core. Multiple branches in the scaling of flux Richardson number with Rig are found typical for TT, a result having implications to the problem of turbulence parameterization.