Examination of the atmospheric conditions associated with high and low summer ozone levels in the lower troposphere over the eastern Mediterranean

Abstract

Abstract. In order to evaluate the observed high rural ozone levels in the eastern Mediterranean area during summertime, vertical profiles of ozone measured in the period [1994][1995][1996][1997][1998][1999][2000][2001][2002][2003][2004][2005][2006][2007][2008] in the framework of the MOZAIC project (Measurement of Ozone and Water Vapor by Airbus in Service Aircraft) over the eastern Mediterranean basin (Cairo, Tel Aviv, Heraklion, Rhodes, Antalya) were analyzed, focusing in the lower troposphere (1.5-5 km). At first, vertical profiles collected during extreme days with very high or very low tropospheric ozone mixing ratios have been examined together with the corresponding back-trajectories. Also, the average profiles of ozone, relative humidity, carbon monoxide, temperature gradient and wind speed corresponding to the 7 % highest and the 7 % lowest ozone mixing ratios for the 1500-5000 m height layer for Cairo and Tel Aviv have been examined and the corresponding composite maps of geopotential heights at 850 hPa have been plotted. Based on the above analysis, it turns out that the lower-tropospheric ozone variability over the eastern Mediterranean area is controlled mainly by the synoptic meteorological conditions, combined with local topographical and meteorological features. In particular, the highest ozone concentrations in the lower troposphere and subsequently in the boundary layer are associated with largescale subsidence of ozone-rich air masses from the upper troposphere under anticyclonic conditions while the lowest ozone concentrations are associated with low pressure conditions inducing uplifting of boundary-layer air, poor in ozone and rich in relative humidity, to the lower troposphere.

Tropospheric Ozone Assessment Report: Assessment of global-scale model performance for global and regional ozone distributions, variability, and trends

“…Such features include the ozone maximum west of southern Africa over the South Atlantic Ocean (e.g., Jonquières et al, 1998;Sauvage et al, 2006), the mid-Pacific minimum, which describes the well-characterized "wave-1" pattern in the tropics (Thompson et al, 2003;Ziemke et al, 2010), and the summertime free tropospheric ozone maximum over the Eastern Mediterranean (e.g., Kalabokas et al, 2013;Zanis et al, 2014).…”

Volatile organic compounds (VOCs) in photochemically aged air from the eastern and western Mediterranean

“…The varying influences from the westerly and northerly winds make Cyprus an ideal vantage point to examine photochemically processed air from eastern and western Europe. Despite a modest population (1.15 million in 2014 1 ) and few industrial emissions, the EU ozone air quality standard is regularly exceeded Kouvarakis et al, 2002;Gerasopoulos et al, 2005;Kalabokas et al, 2007Kalabokas et al, , 2008Kalabokas et al, , 2013Doche et al, 2014;Kleanthous et al, 2014). The excess ozone is formed in sunlit conditions when volatile organic compounds (VOCs), emitted from countries to the north and west of Cyprus, are oxidized in the gas phase by the atmosphere's primary oxidant, the OH radical in the presence of NO x (NO + NO 2 ; Atkinson, 1990).…”

Oxidation processes in the Eastern Mediterranean atmosphere: Evidence from the Modelling of HO<sub>x</sub> Measurements over Cyprus

“…The atmospheric chemistry over the region is complex with regular exceedances of the European Union (EU) ozone air quality standard (Doche et al, 2014;Kalabokas et al, 2013) and a projected increase of summertime O3 over the Eastern Mediterranean (Lelieveld et al, 2002;Lelieveld and Dentener, 2000). (Lelieveld et al, 2002).…”

“…The atmospheric chemistry over the region is complex with regular exceedances of the European Union (EU) ozone air quality standard (Doche et al, 2014;Kalabokas et al, 2013) and a projected increase of summertime O3 over the Eastern Mediterranean (Lelieveld et al, 2002;Lelieveld and Dentener, 2000). the impact of a plethora of hydrocarbons, nitrogen and sulfur species as well as mineral dust on the atmospheric processing in this part of the world, have attracted several field campaigns (Carslaw et al, 2001;Berresheim et al, 2003).…”