On the extraction of turbulent parameters from atmospheric density fluctuations

Abstract

A standard method to analyze turbulent fluctuations of a scalar tracer such as potential neutral density is to obtain the structure function constant C 2 n from the spectrum and to deduce geophysical relevant parameters from C 2 n . As has been realized earlier, there is a significant drawback in this method because some “constants” are needed which are very difficult to measure and which are therefore only poorly known. In addition, inconsistencies in the constants used also appeared in the literature. In this paper we present a new method to obtain turbulent parameters from the spectra where most of these “constants” are not needed. The basic idea is to fit a spectral model [ Tatarskii , 1971] to the experimental spectrum which comprises both the inertial‐convective and the transition to the viscous‐diffusive subrange. Application of this new method to spectra during the NLC‐91 and DYANA campaign shows good agreement between the model and the data. Exemplary comparison of the energy dissipation rates obtained from C 2 n and from the spectral model shows larger values for the latter with comparatively small difference in one case (DAT13, factor 1.2) and larger deviations in a second flight (NBT5, factor 2.4).