Spatial distribution of aerosol in the troposphere according to the DELICAT project
A.E. Mamontov, O.V. Fedorova, M.E. Gorbunov
A.M. Obukhov Institute of Atmospheric Physics Russian Academy of Sciences, Moscow, Russia
Keywords: lidar, remote sensing, spatial spectra, aerosol density fluctuations, scattering, turbulence
Abstract
The analysis of statistical properties of aerosol density fluctuations can serve a starting point for the study of the random component of wind velocity field. In this paper, we analyze the fluctuations of power of a scattered signal measured by an airborne lidar in the DELICAT (DEmonstration of LIdar based Clear Air Turbulence detection) project experiment. A new method for the study of aerosol clouds based on 2D Fourier transform was proposed. Flight segments with constant altitude, direction, and velocity of aircraft were selected for the analysis. A signal was considered in the coordinate system with the abscissa axis representing the distance from the aircraft to a scattering volume and the ordinate axis representing the aircraft path relative to air mass. In these coordinates, aerosol clouds appear as stripes inclined at an angle of 45°. Spatial spectra of aerosol density fluctuations are obtained. For areas where aerosol is observed, 2D spectra have a peak in the vicinity of the main diagonal of the frequency plane. Their diagonal sections are equal to estimates of 1D spatial spectra of aerosol concentration fluctuations within the following approximations: 1) clouds are stationary on a time scale on the order of 1 min, 2) variations in the direction of the sounding line are negligibly small. The slope of 1D spectra has been estimated.
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