Transcript Slide 1

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
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Covers particle diameter range from 3
nm to 10 μm
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6 aerosol species (including marine
organic matter)
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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
17.7.2015
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Acknowledgements
Funding of this study:
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European Space Agency
ECHAM-HAMMOZ development:
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Academy of Finland
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ETH Zurich
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Max Planck Institut für Meteorologie
Funding of measurements:
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Forschungszentrum Jülich
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French Polar Institute (IPEV)
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University of Oxford
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ACTRIS
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Finnish Meteorological Institute
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EPA
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HEA-PRTLI4
Personal help:
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Mikko Aalto
Data providers:
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Shubha Sathyendrath
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ECMWF
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Salvatore Marullo
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GlobColour
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Nicholas Meskhidze
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AERONET
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EMEP
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IMPROVE
•
ICARE
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ESA Climate Change Initiative
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Aerosol-cci project