1. Calculation of key optical properties of the main anthropogenic aerosols over the Western French coastal Mediterranean Sea
- Author
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Mallet, M., Gomes, L., Solmon, F., Sellegri, K., Pont, V., Roger, J.C., Missamou, T., and Piazzola, J.
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AEROSOLS , *OPTICAL properties , *ALBEDO , *RADIATIVE forcing , *SULFATES , *AMMONIUM , *COASTS - Abstract
Abstract: The main purpose of this study is to provide new estimations of optical properties for different aerosol species (Elemental (EC) and Organic Carbon (OC), sulfate (S), ammonium (AM) and nitrate (N)) over the Western Mediterranean Sea. This study is based on chemical measurements obtained over the French Mediterranean coastal region which were used to calculate the main optical properties (i.e., Mass Extinction Efficiency (MEE), Single Scattering Albedo (SSA) and asymmetry parameter (g)), which are relevant for Regional Climate Models (RCMs). Our results indicate that EC particles display averaged MEE (with associated uncertainty range) of 5.7 (4.6–6.9)m2 g−1 (at 550nm), that is significantly lower than the value generally used (~10m2 g−1) in RCM simulations conducted over this region. Such differences are mainly due to the inclusion of additional coarse modes in our optical calculations, which are not taken into account in RCMs that generally treat only fine EC particles. Concerning organics aerosols, we obtained a mean dry MEE (with associated uncertainty) of 2.7 (1.8–3.6)m2 g−1 (at 550nm) lower than usually (~5–7m2 g−1) referenced in RCMs. We also investigated the possible impact of absorbing brown carbon “Cbrown” in our calculations showing large changes on dry MEE (from 2.7 to 4.5m2 g−1, at 550nm) and SSA (from 0.99 to 0.45, at 550nm) for pure scattering and absorbing Cbrown organics, respectively. Nitrate and ammonium particles, which are not well documented over this region, are characterized respectively by dry mean (and associated errors) MEE of 1 (0.8–1.2)m2 g−1 and 4 (2.4–5.6)m2 g−1 (at 550nm), together with SSA of 0.89 (0.88–0.90) and 0.97 (0.96–0.98) at 550nm. Such proposed values could be used to optimize RCMs over the Mediterranean basin for studying “aerosol-climate” interaction through feedbacks of particles on sea-surface fluxes, and hydrological cycle. [Copyright &y& Elsevier]
- Published
- 2011
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