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Effects of size resolved aerosol microphysics on photochemistry and heterogeneous chemistry Gan Luo and Fangqun Yu ASRC, SUNY-Albany 2015-5-4

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Introduction Aerosol Micro physics Photo chemistry COD Our purposes Build up the relationships among aerosol, droplet/crystal, COD, and tropospheric photochemistry in GEOS-Chem/APM Study how does the new COD parameterization impact photolysis, oxidants and aerosol microphysics in the troposphere Tie et al. (2003): the influence of COD on photolysis and oxidants Liu et al. (2006): assessed the radiative effect of clouds in GEOS-Chem Liu et al. (2009): studied the impacts of different met inputs (GEOS1-STRAT, GEOS-3, and GEOS-4) on tropospheric photochemistry Aerosol impacts: AOD on photolysis; Surface area: heterogeneous chemistry Mattin et al., JGR, 2003 Twomey effect: aerosol impacts COD and albedo Twomey, JAS, 1977 Influence of anthropogenic aerosol on COD and albedo shown by satellite measurements and CTM Schwartz et al., PNAS, 2001

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Simulation of new COD in GEOS-Chem/APM GEOS-Chem: GEOS5.2.0 met inputs, NOxOxhydrocarbonaerosol simulation, UpToDate emission inventories APM: SP, Sea Salt, Dust, BC, POC, coating of SP on primary particles Cloud Optical Depth: Aerosol number droplet/crystal number Effective Radius (Yu et al., ERL, 2013) + In Cloud Water Content In Cloud COD Linear Mean COD, Radiative Mean COD Liquid Cloud: Hu and Stamnes, JC, 1993; Ice Cloud: Fu, JC, 1996 Size distribution, Yu, ACP, 2011CN10 number concentration Yu and Luo, ACP, 2009 CCN0.4 number concentration Yu et al., ACP, 2012

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Comparison of COD (GEOS5 and NewCld) with MODIS and ISCCP Radiative Mean CODLinear Mean COD l = incld CldFraction MODIS: 13.79 GEOS5: 3.7 NewCloud: 11.28 Radiative Mean COD r = incld (CldFraction) 1.5 ISCCP: 4.14 GEOS5: 1.77 NewCloud: 5.44 GEOS5 significantly underestimated COD NewCld In better agreement with observed COD MODIS GEOS5 NewCld ISCCP GEOS5 NewCld

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The difference between COD from GEOS5 and NewCld and the correlation with CCN and CDN number concentration MODIS CDNC: Bennartz, 2007; Gantt et al., 2014

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Impact of COD on Boundary layer photochemistry and aerosol microphysics The Tropics: 30-50% Alaska, Siberia: 20% South Ocean: 20% Tropical clear sky regions: 1-5% PH 2 SO 4 : new particle formation and growth; PLVSOG: particle growth especially over luxuriant vegetation regions The Tropics: 10-30% CCN > CN3 particle growth Alaska, Siberia: 10% South Ocean: Sea salt J(O 1 D) H 2 SO 4 CN3 OH LVSOG CCN0.4

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Impact of COD on photochemistry and aerosol microphysics: view from zonal cross section

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Impact of size resolved aerosol on heterogeneous chemistry

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Summary We developed a new COD parameterization in GEOS-Chem/APM, considering the aerosol indirect effect on clouds. It improves the agreement with observed COD and enable us to consider interactions among aerosol, droplet/crystal, COD, and tropospheric photochemistry. Low layers: COD J(O 1 D), [OH] 1) PH 2 SO 4 nucleation , condensation aerosol # & size 2) PLVSOG condensation aerosol size Vertical cross section: significant backscattering effect above cloud: enhancement; below cloud: reduction changes of atmospheric oxidation capacity and tracers lifetime We use APM simulated surface area instead of bulk aerosol surface and find substantial impacts which depend on seasons.

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The End Thank You !

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LWP, IWP and TWP from GEOS5 (Barahona et al., 2014) CloudSAT (Li et al, 2012) and GEOS5.2.0 Figures are from Barahona et al., GMD, 2014LWP, IWP and TWP from GEOS5.2.0