Aerosol Activity and Hygroscopicity Combined with Lidar Data in the Urban Atmosphere of Athens, Greece in the Frame of the HYGRA_CD Campaign

¹ Laser Remote Sensing Laboratory, National Technical University of Athens, 15780 Athens, GREECE
² School of Earth & Atmospheric Sciences and Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta 30332, GA, USA
³ ERL, INRSTES, N.C.S.R. Demokritos, 15310 Agia Paraskevi, Attiki, GREECE
⁴ IERSD, National Observatory of Athens, Palaia Penteli, GREECE
⁵ ECPL, Department of Chemistry, University of Crete, 71003 Heraklion, GREECE
⁶ ICE-HT, Foundation for Research and Technology, Hellas, 26504 Patras, GREECE

^* Email: kbougioti@gmail.com

Published online: 7 June 2016

Abstract

Measurements of cloud condensation nuclei (CCN) concentrations between 0.2-1.0% supersaturation and aerosol size distribution were performed at an urban background site of Athens during HygrA-CD. The site is affected by local and long-range transported emissions as portrayed by the external mixing of the particles, as the larger ones appear to be more hygroscopic and more CCN-active than smaller ones. Activation fractions at all supersaturations exhibit a diurnal variability with minimum values around noon, which are considerably lower than unity. This reinforces the conclusion that the aerosol is mostly externally mixed between “fresher”, less hygroscopic components with more aged, CCN active constituents.