N. Kalivitis

Evidence of gravity waves into the atmosphere during the March 2006 total solar eclipse

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Evidence of gravity waves into the atmosphere during the March 2006 total solar eclipse C. S. Zerefos, E. Gerasopoulos, I. Tsagouri, B. Psiloglou, A. Belehaki, T. Herekakis, A. Bais, S. Kazadzis, C. Eleftheratos, N. Kalivitis, et al.

Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition

Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment.

Formation and growth of atmospheric nanoparticles in the eastern Mediterranean: Results from long-term measurements and process simulations

Atmospheric new particle formation (NPF) is a common phenomenon all over the world. In this study we present the longest time series of NPF records in the eastern Mediterranean region by analyzing 10 years of aerosol number size distribution data obtained with a mobility particle sizer. The measurements were performed at the Finokalia environmental research station on Crete, Greece, during the period June 2008–June 2018. We found that NPF took place on 27 % of the available days, undefined days were 23 % and non-event days 50 %. NPF is more frequent in April and May probably due to the terrestrial biogenic activity and is less frequent in August. Throughout the period under study, nucleation was observed also during the night. Nucleation mode particles had the highest concentration in winter and early spring, mainly because of the minimum sinks, and their average contribution to the total particle number concentration was 8 %. Nucleation mode particle concentrations were low outside periods of active NPF and growth, so there are hardly any other local sources of sub-25 nm particles. Additional atmospheric ion size distribution data simultaneously collected for more than 2 years were also analyzed. Classification of NPF events based on ion spectrometer measurements differed from the corresponding classification based on a mobility spectrometer, possibly indicating a different representation of local and regional NPF events between these two measurement data sets. We used the MALTE-Box model for simulating a case study of NPF in the eastern Mediterranean region. Monoterpenes contributing to NPF can explain a large fraction of the observed NPF events according to our model simulations. However the adjusted parameterization resulting from our sensitivity tests was significantly different from the initial one that had been determined for the boreal environment. Published by Copernicus Publications on behalf of the European Geosciences Union. 2672 N. Kalivitis et al.: Formation and growth of atmospheric nanoparticles in the eastern Mediterranean

Sources of Atmospheric Aerosols in Heraklion, Crete During Winter Time

The contribution of Black Carbon (BC) to the levels of PM10 was studied in the city of Heraklion, Crete. Measurements were performed at the atmospheric quality measurement station of the Region of Crete at the Heraklion city center during the winter/spring period of 2014–2015 and 2015–2016. Continuous measurements were performed using a beta-attenuation PM10 monitor and a 7-wavelength Aethalometer with a time resolution of 30 and 5 min respectively. For direct comparison to background regional conditions, concurrent routine measurements at the atmospheric research station at Finokalia were utilized as background reference. Analysis of exceedances in the daily PM10 mass concentration (50 µg m−3) showed that the majority of the exceedances was related to long range transport of Saharan dust rather than local sources. However, compared to the Finokalia station it was found that there were 60 % more exceedances in Heraklion, the superimposition of transported pollutants on the local pollution was the reason for the additional exceedance days. Excluding dust events, it was found that the PM10 variability was dependent on the BC abundance, traffic during rush hours in the morning and biomass burning for domestic heating in the evening contributed significantly to PM10 levels in Heraklion.

Simulations of New Particle Formation and Growth Processes at Eastern Mediterranean, with the MALTE-Box Model

Simulations of New Particle Formation (NPF) events observed at Finokalia research station of the University of Crete were performed using MALTE-Box. The MALTE-box is a 0-d model that simulates chemical and aerosol dynamical processes with the use of a size-segregated aerosol model, UHMA (University Helsinki Multicomponent Aerosol Model). Measurements from Finokalia station and results from numerical simulations were used as input data in the model. Specifically, biogenic and anthropogenic emissions were taken from the global three-dimensional chemistry-transport model TM4-ECPL. Α case study was performed, during which an ‘‘event’’ and a ‘‘non event’’ week in August 2012 were simulated. During the ‘‘event’’ week new particle formation was detected at Finokalia station, whereas this didn’t happen during the ‘‘non event’’ week. During the ‘‘event week’’ the simulations of NPF capture the day that NPF is observed. However, they underestimate the growth rate of the newly formed particles when compared to observations. Simulations improve when measurements of monoterpenes at Finokalia station are used as input to the model that computes new particles growth rate by ELVOC and SVOC issued from monoterpenes chemistry.