Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 175-192, 2017
http://www.atmos-chem-phys.net/17/175/2017/
doi:10.5194/acp-17-175-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
04 Jan 2017
New particle formation in the southern Aegean Sea during the Etesians: importance for CCN production and cloud droplet number
Panayiotis Kalkavouras1, Elissavet Bossioli1, Spiros Bezantakos2, Aikaterini Bougiatioti3,7, Nikos Kalivitis3, Iasonas Stavroulas3, Giorgos Kouvarakis3, Anna P. Protonotariou1, Aggeliki Dandou1, George Biskos4,5, Nikolaos Mihalopoulos3,5,6, Athanasios Nenes6,7,8,9, and Maria Tombrou1 1Department of Physics, National and Kapodistrian University of Athens, Athens, 15784, Greece
2Department of Environment, Univ. of the Aegean, Mytilene 81100, Greece
3Env. Chemical Processes Lab., Dept. of Chemistry, Univ. of Crete, Heraklion 71003, Greece
4Fac. of Civil Engineering and Geosciences, Delft Univ. of Technology, Delft 2628 CN, the Netherlands
5Energy Environment and Water Research Center, The Cyprus Institute, Nicosia 2121, Cyprus
6Institute of Env. Research & Sustainable Development, National Observatory of Athens, Palea Penteli 15236, Greece
7School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
8School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
9Institute for Chemical Engineering Science, Foundation for Research and Technology Hellas, Patra 26504, Greece
Abstract. This study examines how new particle formation (NPF) in the eastern Mediterranean in summer affects CCN (cloud condensation nuclei) concentrations and cloud droplet formation. For this, the concentration and size distribution of submicron aerosol particles, along with the concentration of trace gases and meteorological variables, were studied over the central (Santorini) and southern Aegean Sea (Finokalia, Crete) from 15 to 28 July 2013, a period that includes Etesian events and moderate northern surface winds. Particle nucleation bursts were recorded during the Etesian flow at both stations, with those observed at Santorini reaching up to 1.5  ×  104 particles cm−3; the fraction of nucleation-mode particles over Crete was relatively diminished, but a higher number of Aitken-mode particles were observed as a result of aging. Aerosol and photochemical pollutants covaried throughout the measurement period; lower concentrations were observed during the period of Etesian flow (e.g., 43–70 ppbv for ozone and 1.5–5.7 µg m−3 for sulfate) but were substantially enhanced during the period of moderate surface winds (i.e., increase of up to 32 for ozone and 140 % for sulfate). We find that NPF can double CCN number (at 0.1 % supersaturation), but the resulting strong competition for water vapor in cloudy updrafts decreases maximum supersaturation by 14 % and augments the potential droplet number only by 12 %. Therefore, although NPF events may strongly elevate CCN numbers, the relative impacts on cloud droplet number (compared to pre-event levels) is eventually limited by water vapor availability and depends on the prevailing cloud formation dynamics and the aerosol levels associated with the background of the region.

Citation: Kalkavouras, P., Bossioli, E., Bezantakos, S., Bougiatioti, A., Kalivitis, N., Stavroulas, I., Kouvarakis, G., Protonotariou, A. P., Dandou, A., Biskos, G., Mihalopoulos, N., Nenes, A., and Tombrou, M.: New particle formation in the southern Aegean Sea during the Etesians: importance for CCN production and cloud droplet number, Atmos. Chem. Phys., 17, 175-192, doi:10.5194/acp-17-175-2017, 2017.
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Short summary
Concentrations of chemically and size-resolved submicron aerosol particles along with concentrations of gases and meteorological variables were measured at Santorini and Finokalia (central and southern Aegean Sea) during the Etesians. Particle nucleation bursts were recorded. The NPF can double CCN number (at 0.1 % supersaturation), but the resulting strong competition for water vapor in cloudy updrafts decreases maximum supersaturation by 14 % and augments the potential droplet number by 12 %.
Concentrations of chemically and size-resolved submicron aerosol particles along with...
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