A new approach to atmospheric turbulence measurements using HOSE on radar backscattered echoes

Abstract

A Novel approach has been proposed for the measurement of turbulent energy dissipation rate (ε) from Nonlinear index (NLI) based measurements using the Higher Order Spectral Estimation (HOSE) technique. The higher order spectral analysis, also known as Bispectrum, is useful for identifying nonlinearities present in the signals. Earlier studies used Bispectrum measurements to experimentally study the spectral energy transfer due to wavenumber interactions in a turbulent flow, which is briefly discussed in the manuscript. This is one of the main motivations for considering HOSE on Atmospheric signals. The Bicoherence obtained by this method has been applied to the backscattered signals received from the Mesosphere, Stratosphere, and Troposphere (MST) radar, Gadanki. Here we considered both convective and clear air atmospheric observations for the analysis and calculated the Nonlinear Index (which represents the amount of nonlinearity in signals) obtained from the Bicoherence for each range bin. We observed that the nonlinearity index indirectly provides information about turbulent intensity. An empirical relationship between the nonlinear index and turbulent energy dissipation rate has been established through regression models. The results of the turbulence energy dissipation rate (ε) obtained from the nonlinear index based method have been compared with the turbulence energy dissipation rate (ε) obtained from the spectrum width based method.