SAWA experiment—evaluation of dust particles properties by means of lidar and sun-photometer synergic measurements

A method of retrieving basic informations about aerosol from synergic measurements of a multi-wavelength depolarisation lidar and sun-photometer is proposed. Lidar signals are inversed with a modified Klett-Fernald algorithm. Independent information on total optical depth of aerosol allows to reduce the number of assumptions needed to run an inversion procedure. The procedure was first used during SAWA measurement campaign in Warsaw, spring 2005, to characterise the particles of Sahara dust, drifting over Poland with a southern-eastern wind (13-14 April). In this particular case of the mineral dust aerosol an additional assumption that particles are represented by ensembles of randomly oriented, identical spheroids was adopted. Then the transition matrix (T-matrix) algorithm was used in order to estimate the size and aspect ratio of the the observed aerosol. The estimated modal radii of the mineral dust particles was in the range of 0,15 – 0,3 micrometers, aspect ratios were either smaller than 0,7 or larger than 1,7.