A note on the testing of a Monte Carlo procedure for evaluating multiple-scattering effects on lidar returns from clouds

A Monte Carlo code for calculating lidar returns from clouds in regime of multiple scattering is tested, by comparing its results pertaining to second order of scattering with those obtained by using an analytic formula developed in a completely different way. For obtaining second order of scattering all the essential parts of the Monte Carlo code are employed. Thus the very good agreement between the results of the two procedures, which have been found in a series of different situations of scattering media, has to be considered as a positive test of the Monte Carlo code reliability

Parametric and non-parametric estimation of speech formants: Application to infant cry

The present paper addresses the issue of correctly estimating the peaks in the speech envelope (formants) occurring in newborn infant cry. Clinical studies have shown that the analysis of such spectral characteristics is a helpful noninvasive diagnostic tool. In fact it can be applied to explore brain function at very early stages of child development, for a timely diagnosis of neonatal disease and malformation. The paper focuses on the performance comparison between some classical parametric and non-parametric estimation techniques particularly well suited for the present application, specifically the LP, ARX and cepstrum approaches. It is shown that, if the model order is correctly chosen, parametric methods are in general more reliable and robust against noise, but exhibit a less uniform behaviour than cepstrum. The methods are compared also in terms of tracking capability, since the signals under study are nonstationary. Both simulated and real signals are used in order to outline the relevant features of the proposed approaches

Simulated Multiply-Scattered Lidar Returns from Nonspherical Particles

Presents an investigation of the characteristics of multiply-scattered lidar returns from homogeneous layers of monodispersed nonspherical particles. A Monte Carlo procedure has been employed to simulate lidar measurements. Total detected power as well as depolarization of the detected signal have been calculated for a variety of particle deformations and orientations, fields of view (FOVs) of the receiver and optical thicknesses of the medium. It has been found that in certain cases multiply-scattered photons cause a decrease in the depolarization of the received light. The results have been checked, for double scattering, by comparing them with the outcome of analytical calculations

LIDAR multiple scattering from clouds

Multiple-scattering LIDAR return calculations obtained by seven different models for the same specified numerical experiment are compared. This work results from an international joint effort stimulated by the workshop group called MUSCLE for MUltiple SCattering Lidar Experiments. The models include approximations to the radiative-transfer theory, Monte-Carlo calculations, a stochastic model of the process of multiple scattering, and an extension of Mie theory for particles illuminated by direct and scattered light. The model solutions are similar in form but differ by up to a factor of 5 in the strength of the multiple-scattering contributions. Various reasons for the observed differences are explored and their practical significance is discussed