New Particle Formation in the South Aegean Sea during the Etesians: importance for CCN production and cloud droplet number

P. Kalkavouras, E. Bossioli, S. Bezantakos, A. Bougiatioti, N. Kalivitis, I. Stavroulas, G. Kouvarakis, A. P. Protonotariou, A. Dandou, G. Biskos, N. Mihalopoulos, A. Nenes (+1 others)
2016 Atmospheric Chemistry and Physics Discussions  
We examine the concentration levels and size distribution of submicron aerosol particles along with the concentration of trace gases and meteorological variables over the central (Santorini) and south Aegean Sea (Crete) from 15 to 28 July 2013, a period that includes Etesian events and moderate northern winds. Particle nucleation bursts were recorded during the Etesian flow at both stations, with those observed at Santorini reaching up to 1.5 × 10<sup>4</sup> particles
more » ... On Crete (at Finokalia station), the fraction of nucleation-mode particles was diminished, but a higher number of Aitken-mode was observed as a result of the downward mixing and photochemistry. Aerosol and photochemical pollutants covaried throughout the measurement period: lower concentrations were observed during the period of strong Etesian flow (e.g. 43&amp;ndash;70 ppbv for ozone, 1.5&amp;ndash;5.7 μg m<sup>&amp;minus;3</sup> for sulfate), but were substantially enhanced during the period of moderate winds (i.e., increase of up to 32 % for ozone, and 140 % for sulfate). To understand how new particle formation (NPF) affects cloud formation, we quantify its impact on the CCN levels and cloud droplet number concentration. 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 in the region.
doi:10.5194/acp-2016-330 fatcat:dcsit2ycb5bivdwddnw53afmfq