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Direct and Indirect Effects of Sea Spray Aerosol using a Source Function Encapsulating Wave State A.-I. Partanen, E. M. Dunne, T. Bergman, A. Laakso, H. Kokkola, J. Ovadnevaite, L. Sogacheva, D. Baisnée, J. Sciare, A. Manders, C. O’Dowd, G. de Leeuw, and H. Korhonen Earth Observation for Ocean-Atmosphere Interactions Science 2014, Frascati, Italy 1. Implement the OSSA source function into the global aerosolclimate model ECHAM-HAMMOZ 2. Calculate global sea spray aerosol emissions and burden 3. Evaluate the model against satellite and other measurements 4. Calculate direct and indirect radiative effects of sea spray aerosol consisting of sea salt and primary marine organic matter GOALS OF THE STUDY Global aerosol-climate model ECHAMHAMMOZ (ECHAM5.5-HAM-SALSA) • The atmospheric core model ECHAM is developed at Max Planck Institute for Meteorology • Horizontal resolution is about 1.9°×1.9° (~200 km × 200 km) • The model meteorology is nudged towards ERA Interim data in the runs of this project Model implementation Aerosol model HAM N, m 3 nm 30 nm Sub-range 1 SU, OC N • Developed at the Finnish Meteorological Institute • Covers particle diameter range from 3 nm to 10 μm • 6 aerosol species (including marine organic matter) • Microphysical core SALSA calculates aerosol microphysical processes • Aerosol-cloud interactions calculated online • Aerosols’ interaction with SW and LW radiation calculated online 700 nm 10 um dp Sub-range 2 Sub-range 3 SU, OC, BC, DU, SS, MO SS Soluble SU, OC, BC, DU DU Insoluble DU, WS Insoluble, soluble coating Sea spray flux for 30 nm < Ddry < 6 μm is calculated from the OSSA source function and for 6 μm < Ddry < 10 μm from matched Monahan (1986) Sea spray flux for 30 nm < Ddry < 6 μm is calculated from the OSSA source function and for 6 μm < Ddry < 10 μm from matched Monahan (1986) Organic matter only in 30 nm < Ddry < 700 nm Organic mass fraction of sea spray is calculated as a function of Chlorophyll-a concentration (with 8-day lag) and wind speed following Rinaldi et al. (2013) • Primary marine organic matter is prescribed to have • Low hygroscopicity in subsaturated conditions • High cloud-activation efficiency Figure: Organic fraction of sea spray • Chlorophyll-a concentration was obtained from GlobColour website Wave heigh data were obtained from ECMWF Comparison of aerosol concentrations to in-situ measurements RESULTS Submicron sea salt concentration was captured well by the model (middle panel) at Mace Sulfate (PM1) Head. Sea salt (PM1) Figure a) Sulfate (PM1) b) Sea salt (PM1) c) Organic matter (PM1) Organic matter (PM1) Global sea spray aerosol emissions and burden RESULTS Emissions and burdens are on the low-side of previous estimates Model run SS emission PMOM emission SS burden PMOM burden (Tg yr-1) (Tg yr-1) (Tg) (Gg) ossa-ref 805 (378-1233) 1.1 (0.5-1.8) 2.9 (1.2-4.6) 9.0 (3.5-14.6) default-salt 7229 0 12.9 0 Other sea spray aerosol source functions predict typically much higher global emissions of sea salt between about 2000- 12 000 Tg yr-1 (Tsigaridis et al. 2013) and global emissions of PMOM 2.8-76 Tg yr-1 (Gantt et al., 2011; Vignati et al., 2010; Mezkhidze et al., 2011; Tsigaridis et al., 2013). Comparison of aerosol optical depth againsts satellite measurements RESULTS AOD is underestimated in most of the ocean area compared to satellite-estimates But mean error is slightly lower (35% vs. 41%) with the new source function than the model default source function OSSA Final Meeting, ESRIN, Frascati, Italy Figure a) AOD from PARASOL satellite b) Modelled AOD with new source function c) Modelled AOD with model default source function Radiative effects of sea spray aerosol RESULTS Sea salt Direct effect of sea salt is negative (global mean -0.5 W m-2 ) Indirect effect is positive (0.3 W m-2 ) Less cloud condensation nuclei and optically thinner clouds Primary marine organic matter have a small negative indirect effect of -0.07 W m-2 Change in cloud droplet number concentration due to primary marine organic matter SUMMARY AND CONCLUSIONS Summary and conclusions • Sea salt emissions are considerably lower than previous estimates • In smaller sizes the modelled sea salt concentrations agree well with in-situ measurements, but they are overestimated in larger sizes • AOD is underestimated in large parts of the ocean, but the error is smaller than with the model default source function • Sea salt is modelled to have a positive indirect effect and PMOM a small negative indirect effect Partanen, A.-I., Dunne, E. M., Bergman, T., Laakso, A., Kokkola, H., Ovadnevaite, J., Sogacheva, L., Baisnée, D., Sciare, J., Manders, A., O'Dowd, C., de Leeuw, G., and Korhonen, H.: Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state, Atmos. Chem. Phys. Discuss., 14, 4537-4597, doi:10.5194/acpd-14-4537-2014, 2014. OSSA Final Meeting, ESRIN, Frascati, Italy 24.5.2017 20 Acknowledgements Funding of this study: • European Space Agency ECHAM-HAMMOZ development: • Academy of Finland • ETH Zurich • Max Planck Institut für Meteorologie Funding of measurements: • Forschungszentrum Jülich • French Polar Institute (IPEV) • University of Oxford • ACTRIS • Finnish Meteorological Institute • EPA • HEA-PRTLI4 Personal help: • Mikko Aalto Data providers: • Shubha Sathyendrath • ECMWF • Salvatore Marullo • GlobColour • Nicholas Meskhidze • AERONET • EMEP • IMPROVE • ICARE • ESA Climate Change Initiative • Aerosol-cci project