Determination of aerosol optical properties with lidar

Determination of aerosol optical properties with lidar: A comparison between algorithms

Floutsi, Athina (TU Delft Civil Engineering and Geosciences; TU Delft Geoscience and Remote Sensing)

Biskos, G. (mentor)
Russchenberg, H.W.J. (graduation committee)
Schmidt-Ott, A. (graduation committee)
Mamali, D. (graduation committee)

Delft University of Technology

2018-05-30

Lidar systems can provide vertically resolved measurements of the physical and optical properties of the atmospheric particles with high spatiotemporal resolution. In this study, four case studies were analyzed and studied in order to identify the dominant aerosol type over the city of Nicosia in Cyprus: 05 April and 07 April 2015 and 17 April and 21 April 2016. More specifically, vertical profiles of the extinction and backscatter coefficient, Ångström exponent, particle linear depolarization ratio and lidar ratio were manually retrieved from the lidar signal for each case study. For the first case, the main aerosol load was observed in the very lower atmosphere, between 0.25 and 1.25 km. The observed aerosol optical properties indicated the strong presence of maritime aerosols. In the second case study, the aerosol layer was thicker and it was observed between 1.6 and 7 km. Analysis of the optical properties showed that the predominant aerosol types within the PBL were mainly maritime aerosols and aerosols from local sources while higher in the atmosphere the aerosol load consisted of dust mixtures. The third case study, on 17th April 2016, was a relatively clean day and a thin aerosol layer was observed between 0.25 and 2.0 km consisting mainly of maritime and urban aerosols. 21st of April 2016, which was the fourth case study, was a dust event case study. The aerosol load, accumulated between 2.0 and 5.0 km, was characterized as a purely dust layer. The results obtained with the manual retrieval method, were compared with automatically retrieved profiles (provided by the Leibniz Institute for Tropospheric Research) and are in good agreement. More specifically, for the vertically resolved extinction profiles at 532 nm the correlation coefficient values ranged between 0.9784 and 1. The correlation coefficients for the backscatter profiles at 532 nm and 1064 nm ranged from 0.9975 to 0.9986 and from 0.9937 to 0.9996 respectively. The linear particle depolarization ratio profiles also correlated less well with the automatically retrieved one with R ranging from 0.8781 to 0.9889 while similarly, for the volume depolarization ratio profiles the correlation coefficient ranged between 0.7054 to 0.9603.

Aerosol profiles
LIDAR
remote sensing
Cyprus
aerosols
optical properties

http://resolver.tudelft.nl/uuid:6c012d93-4df8-49be-8b04-e09196ba7a37

Student theses

master thesis

© 2018 Athina Floutsi