Estimation of atmospheric optical parameters with simultaneous measurement of vibrational-rotational and purely rotational Raman spectra
S.V. Samoilova, Yu.S. Balin, I.E. Penner
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: aerosol, lidar, elastic and Raman scattering, optical parameters
Abstract
The paper considers the methodological features of determining the optical extinction and backscattering coefficients by simultaneous lidar measurements at the following wavelengths: 532 nm (elastic scattering, ES); 607 nm (vibrational-rotational Raman scattering, RS); 530 nm (purely rotational RS). The ES signal identifies the range of allowable values (RAV) of the coefficients based on the a priori introduction of a physically substantiated lidar ratio. The RS signal at 607 nm, corresponding to a single line of the N2 spectrum, provides a plausible estimate of the ratios in the boundary layer and part of the middle troposphere. The CR signal at 530 nm - a set of N2 and O2 spectrum lines - is characterized by smaller errors and provides a quantitative estimate of the coefficients in all main tropospheric layers. At a wavelength of 530 nm, the differential backscattering cross section depends on height due to temperature changes, which leads to a redistribution of N2 and O2 line intensities. Estimation of parameters from the RS signals is considered plausible when the sought-after coefficients are quantitatively comparable and, at the same time, located within their RAVs. The algorithms is tested using ground-based sensing data on the shore of Lake Baikal in August 2023.
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