Determination of optical and microphysical properties of atmospheric aerosols from multi-wavelength airborne sun photometer (PLASMA).

PhD candidate: Yana Karol

Atmospheric aerosols still represents one of the greatest uncertainty in the study of the processes of climate change. The diversity of aerosol sources and their formation mechanisms make the spatial distribution of aerosols very inhomogenous and requires numerous instruments and different approaches for their analysis.

A new multi-wavelength airborne sun photometer PLASMA (Photomètre Léger Aéroporté pour la Surveillance des Masses d’Air) developed in the Laboratory of Atmospheric Optics, Lille University of Sciences and Technologies allows providing on-board measurements of aerosol optical depth over a wide (0.34 − 2.25 μm) spectral range and at different altitudes (Karol et al., 2013). The information of vertical distribution of aerosol optical properties can be then used to validate the lidar processing algorithms. Moreover, it is possible to retrieve from PLASMA measurements the size distribution of the aerosol particles at different levels. Also, the instrument can be installed on an automobile in order to measure the horizontal profiles of AOT.
This study is dedicated to characterization and calibration of PLASMA and to the analysis of several data sets. Numerous ground-based (Lille, Izan ̃a, Beijing, Wash- ington, Dakar, Cagliari), airborne (Lille, Dakar) and automobile (Izan ̃a, Wash- ington) measurements were held and compared with other instruments (sun pho- tometers, lidars).
Sensitivity study of the Dubovik’s inversion algorithm (Dubovik and King, 2000; Holben et al., 1998) showed that it is possible to get the particle’s size distri- bution from only AOD measurements in the range of 0.34 − 1.64 μm (in some cases 0.34 − 1.02 μm) assuming a value of the refractive index within a limited domain. Airborne PLASMA measurements were inverted and size distributions of the aerosol particles were obtained at different altitudes. This new information is helpful to better understand the formation and spatial distribution of aerosols in the atmosphere.

Laboratories: co-tutelle LOA/LOSM