G. Kouvarakis

Temporal variations of surface regional background ozone over Crete Island in the southeast Mediterranean

The first year-round observations of seasonal and diurnal variations of background ozone at a coastal site on Crete Island in the southeast Mediterranean area are presented here. They point out (1) the existence of a well-defined seasonal cycle with maximum during summer months, (2) the presence of elevated O 3 levels (up to 80 ppbv) during daytime and over time periods of several days, and (3) the dependence of O 3 mixing ratios on air mass origin. Comparison with three-dimensional chemistry transport model results shows that during summer the measured O 3 values exceed the calculated by 10-20 ppbv. Inclusion of biomass burning and biogenic volatile organic emissions in the model could partly offset the discrepancy between model results and observations.

Ozone variability in the marine boundary layer of the eastern Mediterranean based on 7-year observations

also observed with a decline of 1.64 ± 0.15 ppbv yr � 1 , or 3.1% per year. The sharp decline of ozone during the first 5 years (i.e., 3.4 ± 0.2 ppbv yr � 1 or 5.6% per year for 1998– 2002) has been succeeded by an abrupt increase in 2003 (to the 1999 ozone levels), followed by a return to the ‘‘regular’’ ozone declining levels in 2004. The rates of the decline were higher for the spring and summer concentrations. In parallel with the ozone decline, a shift of the maximum ozone concentrations from summer to spring, attributed to a continuous decrease of the summer ozone concentrations, was also observed, with the year 2002 presenting a clear spring maximum. The decline of ozone and the shift of its maximum to spring could be related to the reduction of ozone precursors that occurred both in western/central and eastern European countries. The severe weather phenomena that influenced mainly central Europe in summer 2002 have also affected ozone measurements at Finokalia, since the induced meteorological disturbance caused the prevalence of NW winds instead of the dominant NE flow.

On the importance of atmospheric inputs of inorganic nitrogen species on the productivity of the Eastern Mediterranean Sea

To assess the importance of the atmospheric deposition of nitrogen (N) on the productivity of the eastern Mediterranean Sea, measurements of both wet and dry deposition of dissolved inorganic nitrogen (DIN) have been performed at a remote coastal area in the island of Crete (Finokalia) during a 3-year period (1996–1999). The estimation of dry deposition of DIN is based on measurements of both gaseous (HNO3 and NH3) and particulate phase (NO3− and NH4+) nitrogen compounds. The results of the wet and dry deposition obtained at Finokalia have been compared with data of particulate organic nitrogen (PON) obtained during two yearly (1994–1995 and 1997–1998) surveys (CINCS and MATER) in the Cretan Sea by using sediment traps deployed at 200 and 500 m depths. Our results show that the atmospheric deposition of DIN can account for up to 370% of the measured PON in the sediment traps, indicating that atmospheric pathway alone can sufficiently account for the measured new nitrogen production. On the basis of the primary productivity induced by the imported DIN and the productivity of the southeastern Mediterranean derived from in situ measurements a mean f ratio of 0.24 is calculated indicating that from the N point of view, the eastern Mediterranean can no longer be considered as among the most oligotrophic seas of the world. Other elements, most probably phosphorus (P), can account for the oligotrophic character of the eastern Mediterranean Sea. To our knowledge this is the first attempt to understand the role of the atmospheric input of nitrogen on the productivity of the eastern Mediterranean Sea.

Carbonaceous and ionic compositional patterns of fine particles over an urban Mediterranean area

A carefully designed experimental study based on the monitoring of fine airborne particles, was carried out at three different locations (suburban background, traffic-industrial, coastal background) of an urban Mediterranean area, the Athens Basin. Understanding of the PM(2.5) and PM(1) nature has an important policy implication. In total, five hundred and nineteen samples were chemically analyzed with respect to carbonaceous (organic/elemental carbon) and ionic (NH(4)(+), K(+), Mg(2+), Ca(2+), NO(3)(-), Cl(-), SO(4)(2-)) species. The dataset consists one of the very few in the Mediterranean which simultaneously deals with the carbonaceous and ionic components of fine aerosol fractions, especially for PM(1). Daily PM(2.5) averages often exceeded the E.U. limit values, with their mass being mainly composed of PM(1). The most important constituents of secondary particles were SO(4)(2-) and organic carbon, with both accounting for 56.4%-64.3% and 60.5%-62.3% of the total PM(2.5) and PM(1) mass, respectively. Regional sources, marine/crustal elements, combustion sources and traffic were indicated by factor analysis as the greatest contributors to the mass of both PM(2.5) and PM(1) fractions, accounting for 85.3% and 83.6%, respectively of the total variance in the system. It is worthy to note, the key role of the prevailing atmospheric conditions to the configuration of the obtained picture of the particulate pollution.

Simulated air quality and pollutant budgets over Europe in 2008

Major gaseous and particulate pollutant levels over Europe in 2008 have been simulated using the offline-coupled WRFCMAQ chemistry and transport modeling system. The simulations are compared with surface observations from the EMEP stations, ozone (O3) soundings, ship-borne O3 and nitrogen dioxide (NO2) observations in the western Mediterranean, tropospheric NO2 vertical column densities from the SCIAMACHY instrument, and aerosol optical depths (AOD) from the AERONET. The results show that on average, surface O3 levels are underestimated by 4 to 7% over the northern European EMEP stations while they are overestimated by 7-10% over the southern European EMEP stations and underestimated in the tropospheric column (by 10-20%). Particulate matter (PM) mass concentrations are underestimated by up to 60%, particularly in southern and eastern Europe, suggesting underestimated PM sources. Larger differences are calculated for individual aerosol components, particularly for organic and elemental carbon than for the total PM mass, indicating uncertainty in the combustion sources. Better agreement has been obtained for aerosol species over urban areas of the eastern Mediterranean, particularly for nss-SO4(2), attributed to the implementation of higher quality emission inventories for that area. Simulated AOD levels are lower than the AERONET observations by 10% on average, with average underestimations of 3% north of 40°N, attributed to the low anthropogenic emissions in the model and 22% south of 40°N, suggesting underestimated natural and resuspended dust emissions. Overall, the results reveal differences in the model performance between northern and southern Europe, suggesting significant differences in the representation of both anthropogenic and natural emissions in these regions. Budget analyses indicate that O3 and peroxyacetyl nitrate (PAN) are transported from the free troposphere (FT) to the planetary boundary layer over Europe, while other species follow the reverse path and are then advected away from the source region.

The GLAM Airborne Campaign across the Mediterranean Basin

AbstractThe Gradient in Longitude of Atmospheric Constituents above the Mediterranean Basin (GLAM) airborne campaign was set up to investigate the summertime variability of gaseous pollutants, greenhouse gases, and aerosols between the western (∼3°E) and eastern (∼35°E) sections of the Mediterranean basin as well as how this connects with the impact of the Asian monsoon anticyclone on the eastern Mediterranean in the mid- to upper troposphere (∼5–10 km). GLAM falls within the framework of the Chemistry–Aerosol Mediterranean Experiment (ChArMEx) program. GLAM used the French Falcon-20 research aircraft to measure aerosols, humidity, and chemical compounds: ozone, carbon monoxide, methane, and carbon dioxide. GLAM took place between 6 and 10 August 2014, following a route from Toulouse (France) to Larnaca (Cyprus) and back again via Minorca (Spain), Lampedusa (Italy), and Heraklion (Crete, Greece). The aircraft flew at an altitude of 5 km on its outbound journey and 10 km on the return leg. GLAM also collec...

Physical and Chemical Processes of Polluted Air Masses During Etesians: Aegean-Game Airborne Campaign – An Outline

Gaseous species and aerosol size distribution and chemical composition within the boundary layer during the Etesians is investigated, based upon airborne measurements, over the Aegean Sea, from Crete to Limnos islands (29/8–8/9 2011, Aircraft_BAe146–FAAM). Three flights of a similar route covered the eastern and western parts of the Aegean Sea. Two flights were performed on the same day to study the impact of the diurnal cycle. The sorties involved horizontal tracks mainly at 150 m a.s.l. and above the aerosol layer, at 2.5 km a.s.l., and profiles up to 4.5 km near the ground stations of Crete and Limnos and the Central Aegean Sea. Marked variations were detected in the vertical structure of aerosols and thermodynamic variables between the eastern and western segments flown around the Aegean. Several discrete aerosol layers, separated by a clean slot, containing particles of different chemical composition were observed, with sulfates and organics being the dominant components. CO concentrations ranged from 80 ppb above the mixing layer, up to 140 ppb near the surface. O3 ranged between 50 and 75 ppb, with higher values observed at surface upwind of Finokalia and in the mixing layer in Central and Northern Aegean Sea.

Evaluation of CALIPSO’s Aerosol Classification Scheme During the ACEMED Experimental Campaign Over Greece: The Case Study of 9th of September 2011

In order to assess the validity of CALIPSO’s aerosol classification scheme, an experimental campaign called ACEMED (Evaluation of CALIPSO’s aerosol classification scheme over Eastern Mediterranean) has been organized over Greece on September 2011. In this study, we concentrate on the characterization of the aerosol load over Greece on 9th of September, using advanced in-situ aircraft instrumentation (onboard the FAAM-Bae146 aircraft of the UK Met Office). The analytical evaluation of CALIPSO’s aerosol-type classification scheme that is performed using synchronous/collocated satellite/airborne measurements, show a qualitatively reasonable performance of the CALIPSO’s aerosol classification scheme in the complex aerosol environment of the case under study, where smoke, continental, urban and dust aerosol components are present.

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.