Geometrical characteristics of desert dust layers over Thessaloniki estimated with backscatter/Raman lidar and the BSC/DREAM model

Abstract

In this study, we present a multiyear study of Saharan dust intrusions over Thessaloniki, Greece. Observations were performed at Thessaloniki with a combined Raman/elastic lidar system from January 2001 to December 2006 in the framework of European Aerosol Research Lidar Network (EARLINET). During this period we collected a dataset of 33 Raman/lidar observations when Saharan dust was present in the free troposphere over Thessaloniki. To identify the origin of the observed aerosol layer we used 4-day backward trajectories using the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model at several altitudes. First, we identify the base and the top of the desert dust layers from the lidar measurements. As long as the boundaries of the dust layers are identified, we calculate the mean optical properties and vertically integrated optical properties within the layers. In the second part of the study, an attempt to validate Dust Regional Atmospheric Modelling (DREAM) simulations is made in terms of aerosol extinction profiles. The median of the base of the dust layers over Thessaloniki as determined by the lidar measurements was found around 2 km, whereas the median of the geometrical centre of the dust layers was found around 3.5 km. Comparisons of modelled and measured aerosol extinction coefficients show that the average geometrical characteristics of the Saharan dust layers are well captured by the model simulations.

Acknowledgements

The financial support for the improvement of the EARLINET infrastructure by the European Commission under grant RICA-025991 is gratefully acknowledged. The author also acknowledges the assistance of Dr. Carlos Pérez for the use of DREAM simulations and Dr. Vasilis Amiridis and Dr. Elina Giannakaki for their assistance in the analysis of the lidar measurements.