Intercontinental transport of biomass burning pollutants over the Mediterranean Basin during the summer 2014 ChArMEx-GLAM airborne campaign

Abstract

Abstract. The Gradient in Longitude of Atmospheric constituents above the Mediterranean basin (GLAM) campaign was set up in August 2014, as part of the Chemistry and Aerosol Mediterranean Experiment (ChArMEx) project. This campaign aimed to study the chemical variability of gaseous pollutants and aerosols in the troposphere along a west–east transect above the Mediterranean Basin (MB). In the present work, we focus on two biomass burning events detected at 5.4 and 9.7 km altitude above sea level (a.s.l.) over Sardinia (from 39∘12′ N–9∘15′ E to 35∘35′ N–12∘35′ E and at 39∘30′ N–8∘25′ E, respectively). Concentration variations in trace gas carbon monoxide (CO), ozone (O3) and aerosols were measured thanks to the standard instruments on board the Falcon 20 aircraft operated by the Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) and the Spectromètre InfraRouge In situ Toute Altitude (SPIRIT) developed by LPC2E. Twenty-day backward trajectories with Lagrangian particle dispersion model FLEXPART (FLEXible PARTicle) help to understand the transport processes and the origin of the emissions that contributed to this pollution detected above Sardinia. Biomass burning emissions came (i) on 10 August from the North American continent with air masses transported during 5 days before arriving over the MB, and (ii) on 6 August from Siberia, with air masses travelling during 12 days and enriched in fire emission products above Canada 5 days before arriving over the MB. In combination with the Global Fire Assimilation System (GFAS) inventory and the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite fire locations, FLEXPART reproduces well the contribution of those fires to CO and aerosols enhancements under adjustments of the injection height to 10 km in both cases and application of an amplification factor of 2 on CO GFAS emissions for the 10 August event. The chemistry transport model (CTM) MOCAGE is used as a complementary tool for the case of 6 August to confirm the origin of the emissions by tracing the CO global atmospheric composition reaching the MB. For this event, both models agree on the origin of air masses with CO concentrations simulated with MOCAGE lower than the observed ones, likely caused by the coarse model horizontal resolution that yields the dilution of the emissions and diffusion during transport. In combination with wind fields, the analysis of the transport of the air mass documented on 6 August suggests the subsidence of CO pollution from Siberia towards North America and then a transport to the MB via fast jet winds located at around 5.5 km in altitude. Finally, using the ratio ΔO3 ∕ ΔCO, the plume age can be estimated and the production of O3 during the transport of the air mass is studied using the MOCAGE model.

Multiyear Typology of Long-Range Transported Aerosols over Europe

“…The northern and northeastern circulation types were responsible for Continental and Continental Polluted aerosols, since the air masses cross "the black triangle". Western and northwestern circulations were responsible for long-range transport of Smoke particles [49][50][51]. Southwestern circulations were mainly responsible for Dust particles and for Marine/Cloud aerosols.…”

“…In addition, fire events were recorded in western, central, and northern Europe during 2011 and 2013-2018. Smoke particles of North American forest fire origin were reported over the Mediterranean Basin in 2013 [49,50] and 2014 [51], over western Europe in 2017 [56], over northern Europe in 2016 [55], and over central Europe in 2013 [47,52] and 2015 [53].…”

Summertime surface PM<sub>1</sub> aerosol composition and size by source region at the Lampedusa island in the central Mediterranean Sea

“…Previous long-term observations of the chemical composition of aerosol in the Mediterranean have shown that PM 10 (particulate mass with aerodynamic diameter less than 10 µm) is composed of secondary ammonium sulfate, primary and secondary organic aerosol from fossil fuels or biogenic origins, with contributions from natural aerosols from the Sahara and sea spray (Bove et al, 2016;Koulouri et al, 2008;Schembari et al, 2014;Calzolai et al, 2015). Mineral and sea salt contributions are significantly lower in PM 2.5 particle fraction (Querol et al, 2009a).…”

“…Positive matrix factorization (PMF; Paatero, 1997;Paatero and Tapper, 1994) has proved to be a useful statistical tool in identifying aerosol sources or ageing processes of organics. The source apportionment of PM 2.5 and PM 10 over the Mediterranean, from the PMF method, has been investigated in recent works and showed a large spatial variability in source contributions (Becagli et al, 2012(Becagli et al, , 2017Calzolai et al, 2015;Amato et al, 2016;Diapouli et al, 2017). The PMF approach was also used to study the aerosol source and ageing processes by utilizing the complex nature of organic aerosol in the Mediterranean (e.g.…”

Summertime surface PM<sub>1</sub> aerosol composition and size by source region at the Lampedusa island in the central Mediterranean Sea

“…Furthermore, biomass burning aerosol has frequently been observed over the basin, in particular the dry season in summer when forest fires are more common (Pace et al, 2005). Long-ranged plumes from north American fires have also been observed at high altitudes (Formenti et al, 2002;Ortiz-Amezcua et al, 2014;Brocchi et al, 2018;Ancellet et al, 2016).…”