THE LOCAL EFFECT OF INTERMITTENCY ON THE INERTIAL SUBRANGE ENERGY-SPECTRUM OF THE ATMOSPHERIC SURFACE-LAYER

Orthonormal wavelet expansions are applied to atmospheric surface laye r velocity measurements. The effect of intermittent events on the ener gy spectrum of the inertial subrange is investigated through analysis of wavelet coefficients. The local nature of the orthonormal wavelet t ransform in physical space makes it possible to identify a relationshi p between the inertial subrange slope of the local wavelet spectrum an d a simple indicator (i.e. the local variance of the signal) of local intermittency buildup. The slope of the local wavelet energy spectrum in the inertial subrange is shown to be sensitive to the presence of i ntermittent events. During well developed intermittent events (coheren t structures), the slope of the energy spectrum is somewhat steeper th an -5/3, while in less active regions the slope is found to be flatter than -5/3. When the slopes of local wavelet spectra are ensemble aver aged, a slope of -5/3 is recovered for the inertial subrange.