Spatial and temporal variability of tropospheric ozone (O₃) in the boundary layer above the Aegean Sea (eastern Mediterranean)

Abstract

[1] To study the spatial and temporal variability of tropospheric ozone in the marine boundary layer over the Aegean Sea (eastern Mediterranean), an O 3 analyzer has been installed onboard of a passenger vessel traveling on a regular basis in the Aegean Sea (from Heraklion/Crete 35°30 0 N, 25°13 0 E to Thessaloniki 40°64 0 N, 22°97 0 E) during a period of 14 months (August 1999 to November 2000. In addition, O 3 data have been obtained on a daily basis at the regional background station of Finokalia (Crete; 35°30 0 N, 25°70 0 E) since September 1997, short-term measurements of O 3 were performed over Crete during the PAUR II campaign (May 1999), and the first O 3 data from a rural area (40°32 0 N, 23°50 0 E) close to Thessaloniki at the north of Greece have been collected from March 2000 to January 2001. This survey extensive points out the existence of a welldefined seasonal cycle in boundary layer O 3 with maximum in summer both above the Aegean Sea and at Finokalia. However, the seasonal signal (defined as the summer/winter ratio) is not constant and varies as a function of air mass origin from 1.33 to 1.15 for the N-NE and SW-S sectors, respectively, in line with the geographical location of the O 3 precursor sources. Our data show the absence of any significant longitudinal gradient over Crete at least during spring and autumn and the absence of significant latitudinal gradient between the north and south Aegean Sea during all seasons for air masses having similar origin. The above results indicate that long-range transport is the main factor accounting for the elevated O 3 levels above the eastern Mediterranean Sea. Thus (1) O 3 data from Finokalia, where the longest time series are available for the area, have regional significance and (2) over the entire Aegean basin, ozone values are above the 32 ppbv European Union (EU) phytotoxicity limit throughout the year and above the 53 ppbv EU health protection limit most of the time during the dry season of the year. The very significant correlation between black carbon (BC) and O 3 observed during an intensive campaign in May 2000 provides an indication that the high O 3 concentrations at Finokalia resulted from ageing of air masses strongly affected by combustion processes.

The total solar eclipse of March 2006: overview

“…The area under study is characterized by particularly enhanced level of pollutants by means of ozone Kouvarakis et al, 2002;Kondratyev and Varotsos, 2002;Gerasopoulos et al, 2005;2006a) and particulate matter (Gerasopoulos et al, 2003(Gerasopoulos et al, , 2006b) that also influence the fraction of solar irradiance reaching the surface Papayannis et al, 1998;Varotsos et al, 2001). Total solar eclipses enable the evaluation of our understanding of air pollution build-up and of the response of the gas-phase chemistry of photo-oxidants during a drastic perturbation in solar radiation.…”

A 10-year study of background surface ozone concentrations on the island of Gozo in the Central Mediterranean

“…In the Mediterranean, the background surface ozone mixing ratios are the highest in Europe (Kouvarakis et al 2000(Kouvarakis et al , 2002Gerasopoulos et al 2005;Nolle et al 2002;Lelieveld et al 2002). According to Nolle et al (2005), the ozone mixing ratio in the Central Mediterranean might have increased by a factor of five over the last century.…”

Aged organic aerosol in the Eastern Mediterranean: the Finokalia Aerosol Measurement Experiment – 2008

“…Previous campaigns combined airborne measurements of particles and gases, measurements from ships and measurements at land-based stations including Finokalia, and they showed that measurements at Finokalia are representative of the background Eastern Mediterranean atmosphere (Kouvarakis et al, 2002;Lelieveld et al, 2002). As such, this study provides insights about aerosol in the Eastern Mediterranean as well as the transport and evolution of organic aerosol in general.…”