Retrieval of the tropospheric aerosol microphysical characteristics from the data of multifrequency lidar sensing

S Samoilova,Yu Balin,I Penner,M Sviridenkov,G Kokhanenko,D Nicolae,A Comeron,A Behrendt,A Makoto,A Vassilis,M.P Mccormick,C Senff,F Gibert,U Wandinger,D Balis,I Veselovskii,E Landulfo

doi:10.1051/epjconf/201817605055

S Samoilova, Yu Balin + Show 15 more

Open Access

https://doi.org/10.1051/epjconf/201817605055

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Abstract

Regular lidar measurements of the vertical distribution of aerosol optical parameters are carried out in Tomsk (56°N, 85°E) since April, 2011. We present the results of retrieval of microphysical characteristics from the data of measurements by means of Raman lidar in 2013. Section 2 is devoted to the theoretical aspects of retrieving the particle size distribution function U(r) (SDF) assuming a known complex refractive index m (CRI). It is shown that the coarse fraction cannot be retrieved unambiguously. When estimating U(r) and m together (section 3), the retrieved refractive index is non-linearly related to the optical coefficients and the distribution function, which leads to appearance of different, including false values of m. The corresponding U(r) differs only slightly, so the inaccuracy in m does not essentially affect the retrieval of the distribution function.

Highlights

There is a problem for the lidar data: the parameters of the fine fraction are retrieved well for any regularization matrix, but the parameters of the coarse fraction are estimated ambiguously
The stabilizer order specifies the range of the correct retrieval of the coarse aerosol mode parameters
This in turn leads to biased estimates of U . coarse This clearly expressed dependence of the solution obtained on the restrictions on its smoothness is primarily caused by insufficient information, since for the coarse aerosol mode the spectral dependence of the optical coefficient becomes weak, and they contain only two independent values

Summary

INTRODUCTION

2. RETRIEVAL OF THE SIZE DISTRIBUTION FUNCTION UNDER THE ASSUMPTION OF KNOWN REFRACTIVE INDEX. The determination of the particle size distribution function U (r) (SDF) for the known complex refractive index m (CRI) is reduced to the inversion of a system of linear algebraic equations. The stabilizer order specifies the range of the correct retrieval of the coarse aerosol mode parameters. This in turn leads to biased estimates of U . The biased estimates of Ucoarse are predetermined by the a priori choice of the stabilizer order that in turn can lead to different values both on the abscissa and the ordinate, in particular, it fixes the geometrical mean radius of coarse particles.

A W Wu 1

SIMULTANEOUS RETRIEVAL OF THE SIZE DISTRIBUTION AND REFRACTIVE INDEX