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

Abstract

A 10-year study of surface ozone mixing ratios in the Central Mediterranean was conducted based on continuous ozone measurements from 1997 to 2006 by a background regional Global Atmospheric Watch (GAW) station on the island of Gozo. The mean annual maximum mixing ratio is of the order of 66 ppbv in April-May with a broad secondary maximum of 64 ppbv in July-September. No long-term increase or decrease in the background level of surface ozone could be observed over the last 10 years. This is contrary to observations made in the Eastern Mediterranean, where a slow decrease in the background ozone mixing ratio was observed over the past 7 years. Despite the very high average annual ozone mixing ratio exceeding 50 ppbv-in fact, the highest average background ozone mixing ratio ever measured in Europe-, the diurnal O 3 max /O 3 min index of <1.40 indicates that the island of Gozo is a good site for measuring background surface ozone. However, frequent photosmog events from June to September during the past 10 years with ozone mixing ratios exceeding 90 ppbv indicate that the Central Mediterranean is prone to long-range transport of air pollutants from Europe by northerly winds. This was particularly evident during the so-called "August heatwave" of the year 2003 when the overall ozone mixing ratio was 4.6 ppbv higher than the average of all other 9 months of August since 1997. Air mass back-trajectory analysis of the August 2003 photosmog episodes on Gozo confirmed that ozone pollution originated from the European continent. Regression analysis was used to analyse the 10-year data set in order to model the behaviour of the ozone mixing ratio in terms of the meteorological parameters of wind speed, relative humidity, global radiation, temperature, month of year, wind sector,

Long-term surface ozone variability at Mt. Cimone WMO/GAW global station (2165 m a.s.l., Italy)

“…For the shorter period 1996e2011 no significant O 3 trends were detected at CMN, in fairly good agreement with observations at other high mountain stations in Europe (e.g. Gilge et al, 2010;Logan et al, 2012;Parrish et al, 2012) and in the Mediterranean Islands of Cyprus (Kleanthous et al, 2014) and Malta (Saliba et al, 2008). Ordo nez et al (2007) suggested a strong relationship between stratosphere-to-troposphere exchange and O 3 changes at Alpine stations during 1990s: however no evident correlations existed between O 3 at CMN and long-term SI frequency variability or O 3 SI over the period 1996e2011.…”

“…Not significant long-term O 3 trends were also detected by Saliba et al (2008. O 3 trends have been also calculated on a seasonal basis (DecembereFebruary: DJF; MarcheMay: MAM; JuneeAugust: JJA; SeptembereNovember: SON).…”

Investigation of reactive gases and methane variability in the coastal boundary layer of the central Mediterranean basin

“…Until the year 2014, besides the GAW/WMO Mt. Cimone Global Station (located in Northern Italy), only one other regional GAW/WMO station (El Gozo, Malta, see Saliba et al, 2008) provided longterm information on O 3 variability in this region. Only recently (2014, July), continuous O 3 observations have been started at the regional GAW/WMO station "N. Sarao" at Lampedusa Island (central Mediterranean Sea).…”

Variations in surface ozone and NOx at Kannur: a tropical, coastal site in India

“…One is the direct transport of O 3 from urban areas, and the other is the transport of its precursors like NOx, VOC, CO, CH 4 (NMHC) (Trainer et al 1987), followed by in-situ photochemical O 3 production. In recent years, considerable work has been carried out to explore the influence of surface O 3 on climate change in various parts of the world (Oltmans and Komhyr 1976;Low et al 1992;Mazzeo et al 2005;Filella and Peñuelas 2006;Pudasainee et al 2006;Helmig et al 2007;Geng et al 2008;Saliba et al 2008;Poupkou et al 2009;Sicard et al 2009;Teixeira et al 2009;Geddes et al 2009;Yin Shan et al 2010;Hosseinibalam et al 2010;Banan and Latif 2011;Notario et al 2011). O 3 concentration is influenced by meteorological parameters including wind speed, wind direction, temperature and relative humidity (Lyons and Cole 1976;Aneja and Das 1995) over a location.…”