From Hygroscopic Aerosols to Cloud Droplets: The HygrA-CD Campaign in the Athens Basin—An Overview

The international experimental campaign Hygroscopic Aerosols to Cloud Droplets (HygrA-CD), organized in the Greater Athens Area (GAA), Greece from 15 May to 22 June 2014 provided an unprecedented record of data on aerosols, clouds and meteorology. HygrA-CD brought together different active/passive remote sensing and in situ instrumentation/teams for the purpose of fostering our understanding on the physico-chemical properties of aerosols and their impact on the cloud formation in the lower troposphere, with emphasis on the top of the Planetary Boundary Layer (PBL). The use of well-established numerical weather prediction and atmospheric modeling, such as the Flexible particle (FLEXPART) dispersion model and the Weather Research and Forecasting (WRF) model enabled us to simulate air mass back-trajectories and atmospheric variables in the PBL, such as PBL height (PBLH), relative humidity, wind fields etc. This paper presents the major findings and highlights of the HygrA-CD campaign.