Repository: Freie Universit├Ąt Berlin, Math Department

Multiscale Shear Forcing of Turbulence in the Nocturnal Boundary Layer: A Statistical Analysis

Boyko, V. and Vercauteren, N. (2020) Multiscale Shear Forcing of Turbulence in the Nocturnal Boundary Layer: A Statistical Analysis. Boundary-Layer Meteorology, 177 (2-3). ISSN Electronic: 1573-1472; Print: 0006-8314

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The lower nocturnal boundary layer is governed by intermittent turbulence which is thought to be triggered by sporadic activity of so-called sub-mesoscale motions in a complex way. We analyze intermittent turbulence based on an assumed relation between the vertical gradients of the sub-mean scales and turbulence kinetic energy. We analyze high-resolution nocturnal eddy-correlation data from 30-m tower collected during the Fluxes over Snow Surfaces II field program. The non-turbulent velocity signal is decomposed using a discrete wavelet transform into three ranges of scales interpreted as the mean, jet and sub-mesoscales. The vertical gradients of the sub-mean scales are estimated using finite differences. The turbulence kinetic energy is modelled as a discrete-time autoregressive process with exogenous variables, where the latter ones are the vertical gradients of the sub-mean scales. The parameters of the discrete model evolve in time depending on the locally-dominant turbulence-production scales. The three regimes with averaged model parameters are estimated using a subspace-clustering algorithm which illustrates a weak bimodal distribution in the energy phase space of turbulence and sub-mesoscale motions for the very stable boundary layer. One mode indicates turbulence modulated by sub-mesoscale motions. Furthermore, intermittent turbulence appears if the sub-mesoscale intensity exceeds 10% of the mean kinetic energy in strong stratification.

Item Type:Article
Additional Information:Open Access
Subjects:Mathematical and Computer Sciences
Mathematical and Computer Sciences > Mathematics > Applied Mathematics
ID Code:2480
Deposited By: Ulrike Eickers
Deposited On:30 Nov 2020 10:02
Last Modified:30 Nov 2020 10:02

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