Open AccessPredictability of Dry Convective Boundary Layers: An LES Study
Author(s) -
Siddhartha Mukherjee,
Jerôme Schalkwijk,
Harm J. J. Jonker
Publication year - 2016
Publication title -
journal of the atmospheric sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.853
H-Index - 173
eISSN - 1520-0469
pISSN - 0022-4928
DOI - 10.1175/jas-d-15-0206.1
Subject(s) - predictability , wavenumber , perturbation (astronomy) , reynolds number , boundary layer , physics , convection , lyapunov exponent , growth rate , exponential growth , convective boundary layer , statistical physics , exponential decay , mechanics , mathematics , mathematical analysis , planetary boundary layer , turbulence , geometry , optics , nonlinear system , quantum mechanics
The predictability horizon of convective boundary layers is investigated in this study. Large-eddy simulation (LES) and direct numerical simulation (DNS) techniques are employed to probe the evolution of perturbations in identical twin simulations of a growing dry convective boundary layer. Error growth typical of chaotic systems is observed, marked by two phases. The first comprises an exponential error growth as , with δ0 as the initial error, δ(t) as the error at time t, and Λ as the Lyapunov exponent. This phase is independent of the perturbation wavenumber, and the perturbation energy grows following a self-similar spectral shape dominated by higher wavenumbers. The nondimensional error growth rate in this phase shows a strong dependence on the Reynolds number (Re). The second phase involves saturation of the error. Here, the error growth follows Lorenz dynamics with a slower saturation of successively larger scales. An analysis of the spectral decorrelation times reveals two regimes: an Re-independent regime for scales larger than the boundary layer height and an Re-dependent regime for scales smaller than , which are found to decorrelate substantially faster for increasing Reynolds numbers.