Effects of size resolved aerosol microphysics on photochemistry
and heterogeneous chemistry Gan Luo and Fangqun Yu ASRC,
SUNY-Albany 2015-5-4
Slide 2
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
Slide 3
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
Slide 4
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
Slide 5
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
Slide 6
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
Slide 7
Impact of COD on photochemistry and aerosol microphysics: view
from zonal cross section
Slide 8
Impact of size resolved aerosol on heterogeneous chemistry
Slide 9
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.
Slide 10
The End Thank You !
Slide 11
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
