1. Main regional stakes - Ambient air quality - Chemistry-climate interactions

1. ChArMEx The Chemistry-Aerosol Mediterranean Experiment Contact: francois.dulac@cea.fr • 1. Main regional stakes - Ambient air quality - Chemistry-climate interactions - Impact on ecosystems • 2. Scientific objectives • 3. Interfaces with other projects

2. ChArMEx ChArMEx is the atmospheric chemistry component of the programme: it deals with short-lived tropospheric species

3. Our motivation • The remote Mediterranean atmosphere offers the best combined possibilities • to follow very diverse polluted continental air masses over the basin using satellites (clear sky), background monitoring (observatories) and field campaigns (proximity) • to constrain coupled chemistry-transport and chemistry-climate models ability to simulate all relevant dynamical and chemical processes • In addition, the oligotrophic Mediterranean waters offers the best opportunity to couple atmospheric and marine biogeochemical models • The "Chantier" offers a great opportunity for multidisciplinary coupled approaches (ChArMEx-HyMeX-MERMEX-SICMED)

4. The Mediterranean marine atmosphere is heavily impacted by continental air masses • All types of continental and marine sources of particles and reactive gases Biomass burning Anthropogenic pollution Biogenic emissions Forest fires Forest fires Seasalts Volcanic sulfate Forest fires Marine biogenic emissions Desert dust

5. The Mediterranean: an intense summer photochemistry with a regional ozone peak GOME JJA2000 tropospheric O3 column (DU) PREVAIR 14 July 2006 O3 peak (µg m-3) Summer max.: ~+20 ppb • Example of open questions: • Relative contributions of long-distance transport and regional pollution sources (decreasing European emissions) • Impact on the radiative budget • Long term trends and evolution

6. Continental sources dominate There is a strong maximum in the dry season (no wet scavenging, increased emissions…) The Mediterranean: the regional European maximum in aerosol 2000 annual average aerosol column mass load from AEROCOM models (courtesy of Christiane Textor, after Textor et al., ACP, 2006) • Many open questions: - model components not validated (organics, deposition …) - uncertain trends - impacts not quantified…

7. Enjeu sociétal: améliorer les prévisions de qualité de l’air Summer 2001 (courtesy of K. Sartelet et al.) • Strong biases: major need to improve - desert dust - soot & organics (anthropogenic emissions, emissions of biogenic and semi-volatile compounds, SOA formation)

8. Autre enjeu: quantifier la contribution du transport longue distance Corse Matin, 17 octobre 2008

9. Radiative effects of aerosols dominate those of greenhouse gases at the regional scale Simulations of the difference in radiative flux at TOA between present and pre-industrial period, considering changes in CO2 and sulphate concentrations (Le Treut et al., J. Climate, 1998) Direct forcing of sulphates (min. -2.8, max. 0.2, mean -0.3 W m-2) CO2 forcing (min. 0.0, max. 1.0, mean +0.5 W m-2) • the Mediterranean is among the most affected regions 0 0 Indirect forcing of sulphates (min. -10.4, max. 0.9, mean -0.8 W m-2)

10. The Mediterranean aerosols have a large impact on the solar radiation Pollution aerosol (wo= 0.83-0.89): -66 W m-2 (Roger et al., Atmos. Env., 2006) Aged biomass burning (wo = 0.89): -60 W m-2 (Formenti et al. JGR, 2002) Anthropogenic aerosol (wo= 0.87): -18 W m-2 (Markowicz et al., GRL, 2002) Desert dust (wo= 0.73-0.97): -13, -24, -37 W m-2 Non dust: -37 and -39 W m-2 (Meloni et al., JGR, 2003 and 2004)

11. -15 to -20 W m-2 Direct effect Semi-direct effect 1.5 <heating<2.5 K j-1 gradient >0 convection 20-30 W m-2 Evaporation of low clouds (Ackerman et al., 2000) gradient <0 stratification 0.5 <heating<1.5 K j-1 -40 to -50 W m-2 Modification of the latent heat flux (-20% over the dry season! Ramanathan et al., JGR, 2001) Enjeu sociétal: l’impact probable de la pollution sur le climat régional March 1999 AOT532 =0.6 wo ~0.85 (Léon et al., JGR, 2002)

12. SCAR-A 1993 MINOS 2001 ABC 2005-08 SCAR-C 1994 ACE-2 1997 TARFOX 1996 ACE-3 2001-03 PRIDE 2000 AMMA 2006-07 SHADE 2000 INDOEX 1998-99 SCAR-B 1995 SAFARI 2000 ACE-1 1995 0 Polder Aerosol Index (March 1997) 0.5 Chemistry/aerosol-climate interaction studies are based on regional experiments • The western Med has been neglected up to now EUCAARI Journées IPSL Méditerranée, Jussieu, 25-26 oct. 2007

13. Dissolved iron DFe (nM) May June July August Sept. Oct. Cumulated deposition of DFe from anthropogenic aerosols from Saharan aerosols DDFe (above-below thermocline) A Saharan dust episode: about a half million of tons of dust over the Mediterranean and a deposition of grams per m2 Atmospheric input to surface waters (Dulac et al, Kluwer, 1996) (Bonnet and Guieu, JGR, 2006) • In the period of surface water stratification, deposition explains the dissolved iron enrichment above the thermocline

14. Enjeu sociétal: le dépôt impacte les 1ers éléments de la chaîne trophique marine Impact of atmospheric deposition on marine ecosystems during marine stratification (courtesy of Guieu et al., ANR DUNE) Deppth (m) Seeding the mesocosms with 10 g m-2 of Saharan dust Triplicates for dust addition and for control • Increase in chlorophyll (total duration 9 d)

15. The huge model variability on depositionis a critical problem Global dust aerosol model intercomparison with prescribed mass fluxes, injection height and emitted particle size Dry deposition Wet deposition x 1.9 x 6.8 Adapted from AEROCOM (Aerosol Model Comparison; http://dataipsl.ipsl.jussieu.fr/cgi-bin/AEROCOM/; Textor et al., Atmos. Chem. Phys., 2006 and 2007)

16. ChArMEx scientific objectives • Assessing the present state of the Mediterranean atmospheric environment • Sources and budgets of aerosols and precursors of secondary species? - inventories of natural/anthropogenic sources - long-range transport/regional sources - trends and variability • Chemical and dynamical processes? - chemical transformations, plume aging processes - air mass import/export (3D), orographic and see-breeze effects - stratification and variability in the vertical • Atmospheric deposition? - soluble/insoluble - nutrients (P, N), micronutrients (Fe), contaminants (Hg) • Quantifying the impacts of aerosols and reactive gases • On the surface air quality (long range vs regional contributions) • On the Mediterranean radiative budget and regional climate (SST, evaporation, atmospheric heating, cloud cover, heat waves, photochemistry/oxidizing capacity) • On the surface ecosystems (role of deposition, perturbation of incident radiation) • Predict future evolution

17. ChArMEx interfaces with other projects • ChArMEx-HyMeX: • ChArMEx: radiative budget, impacts of its perturbations on SST, evaporation, atmospheric heating • HyMEx: aerosol-cloud-precipitation interactions • ChArMEx-MERMEX and ChArMEx-SICMED (not investigated yet) : • ChArMEx: atmospheric deposition, perturbation of incoming solar radiation at the surface • MERMEX: impacts on marine biogeochemistry, marine biogenic emissions • SICMED: impacts on terrestrial ecosystems, soil and terrestrial biogenic emissions