Continental pollution in the western Mediterranean basin: vertical profiles of aerosol and trace gases measured over the sea during TRAQA 2012 and SAFMED 2013

Claudia Di Biagio (1) , Lionel Doppler (2, 3, 4) , Cécile Gaimoz (1) , Noël Grand (1) , Gérard Ancellet (4) , Jean-Christophe Raut (4) , Matthias Beekmann (1) , Agnès Borbon (1) , Karine Sartelet (5) , Jean-Luc Attié (6, 7) , François Ravetta (4) , Paola Formenti (1)

1 LISA (UMR_7583) - Laboratoire Interuniversitaire des Systèmes Atmosphériques
2 Freie Universität Berlin
3 DWD - Deutscher Wetterdienst [Offenbach]
4 TROPO - LATMOS
5 CEREA - Centre d'Enseignement et de Recherche en Environnement Atmosphérique
6 CNRM - Centre national de recherches météorologiques
7 LAERO - Laboratoire d'aérologie

In this study we present airborne observations of aerosol and trace gases obtained over the sea in the Western Mediterranean Basin during the TRAQA (TRansport and Air QuAlity) and SAFMED (Secondary Aerosol Formation in the MEDiterranean) campaigns in summers 2012 and 2013. A total of 23 vertical profiles were measured up to 5000 m a.s.l. over an extended area (40–45° N latitude and 2° W–12° E longitude) including the Gulf of Genoa, Southern France, the Gulf of Lion, and the Spanish coast. TRAQA and SAFMED successfully measured a wide range of meteorological conditions which favoured the pollution export from different sources located around the basin. Also, several events of dust outflows were measured during the campaigns. Observations from the present study indicate that continental pollution largely affects the Western Mediterranean both close to coastal regions and in the open sea as far as ~250 km from the coastline. Aerosol layers not specifically linked with Saharan dust outflows are distributed ubiquitously which indicates quite elevated levels of background pollution throughout the Western Basin. The measured aerosol scattering coefficient varies between ~20 and 120 M m−1, while carbon monoxide (CO) and ozone (O3) mixing ratios are in the range of 60–170 and 30–85 ppbv, respectively. Pollution reaches 3000–4000 m in altitude and presents a very complex and highly stratified structure characterized by fresh and aged layers both in the boundary layer and in the free troposphere. Within pollution plumes the measured particle concentration in the Aitken (0.004–0.1 μm) and accumulation (0.1–1.0 μm) modes is between $\sim 100$ and 5000–6000 s cm−3 (standard cm−3), which is comparable to the aerosol concentration measured in continental urban areas. Additionally, our measurements indicate the presence of highly concentrated Aitken layers (10 000–15 000 s cm−3) observed both close to the surface and in the free troposphere, possibly linked to the influence of new particle formation (NPF) episodes over the basin.

Mots clés: ChArMEx

Domaines: Sciences de l'environnement; Physique Atmosphérique et Océanique [physics.ao-ph]

Claudia Di Biagio, Lionel Doppler, Cécile Gaimoz, Noël Grand, Gérard Ancellet, et al.. Continental pollution in the western Mediterranean basin: vertical profiles of aerosol and trace gases measured over the sea during TRAQA 2012 and SAFMED 2013. Atmospheric Chemistry and Physics, 2015, 15 (16), pp.9611-9630. ⟨10.5194/acp-15-9611-2015⟩. ⟨hal-01133230⟩