Transcript Evaluation of GEOS-Chem AOTs: comparisons to satellite data

Evaluation of GEOS-CHEM Aerosol
Optical Thicknesses : comparisons
to satellite data for 2003
S. Generoso & I. Bey
LMCA, EPFL, Lausanne, Switzerland
Acknowledgements : F.M: Bréon (POLDER data),
Q. Li & R. V. Martin (Data for the Mie calculation)
We plan to use GEOS-CHEM to ...
1. Characterize
aerosol
distributions (e.g.
T2 : projet / questions
scientifiq
anthro. vs natural) / focus over the Asian
continent and Pacific/Indian Oceans
2. Investigate processes (e.g.
heights, deposition, transport …)
comparisons with multi
observations (satellites,
ground-based measurements)
emission
The method chosen to start
Year 2003 : Both POLDER & MODIS data
T2 : projet / questions scientifiq
Large interannual aerosol events in Asia during
spring/summer 2003 (to characterize)
Data : POLDER, MODIS, AERONET … (others
are welcome)
GEOS-CHEM
v07-02-03
GEOS-CHEM :: version
version used
v07-02-03
Resolution
2°xfor
2.5°
Modifications
this study :
30
-->levels
AOT @ 550 & 865 nm on-line
GEOS
4
--> biomass
burning emissions for 2003 based on
ATSR fire counts
ATSR fire count and emission inventories
 Adapted from Generoso et al,
ACP, 2003
 Definition of “homogeneous”
regions
 An emission constant (g/detected
fire) computed for each region
ATSR fire counts (night time)
Available 07/96 => 10/03
annual emission used in GEOS-CHEM
(XXX.bioburn. seasonal.geos.2x25)
 Seasonal cycle, Interannual
variations and Spatial distribution
follow satellite observation
 Emitted quantities depend on
the inventories used
Differences introduced in the BB emissions used in
GEOS-CHEM ...
… inT2terms
of/ emitted
quantities :
: projet
questions scientifiq
OC in kg /year (x 1010)
“ATSR”
“CURRENT”
2000
1.70
2.11
2002
2.25
2.67
2003
2.00
2.34 (CLIM)
THIS
STUDY
CURRENTLY USED
IN GEOS-CHEM
v-07-02-03
… in terms
of spatial
distribution
OCPO Emissions JUNE 03
CLIM
1.4 x 108 kg
THIS STUDY
7.3 x 108 kg
kg /month
The POLDER mission
(Polarization and Directionality of the Earth Reflectance)
POLDER-1 : Nov 96 to Jun 97
POLDER-2 : Apr 03 to Oct 03
Total AOT
(Aerosol Optical Thickness)
Classical method - Over ocean only
AOT ~ column aerosol load
(On ADEOS)
Fine mode AOT
Originality : polarization - over
ocean and land
~ column aerosol load in the fine
mode
May 2003
Comparisons to
POLDER AOT :
FINE mode
Sulf + BC + OC + SSac
Overestimate in
Northern Hemisphere
(mainly sulfates over
Europe)
Underestimate in B.B.
regions
Comparisons to
POLDER AOT:
COARSE mode
DUST + SSc
Underestimate in
Bay of Bengal
Dust export to
Atlantic rather
well represented
Conclusions
1. Biomass Burning emissions for 2003 available
May be underestimated
Can be provided when the ATSR data are available (from 96/07 to
03/10)
2. AOT @ 550 & 865 nm available
3. 1st comparisons to satellite data show that there is a
lot to investigate
Overestimation of fine mode AOT in Northern Hemisphere (mainly
sulfates)
 Underestimation of fine mode AOT in BB regions
 Underestimation of coarse mode AOT in Bay of Bengal
 Dust export to Atlantic rather well represented
Additional slides
... in terms of seasonal cycles
T2 : projet / questions scientifiq
Clim
2003 “ATSR”
2002 “ATSR”
OC in kg C
2002 “Current”
month
Spatial distribution … modified
initial
ATSR
98
ATSR
00
Burnt
Area 00
Better agreement with burnt area observations
ATSR vs other biomass burning sat. products
Sahel
North
Australi
a
South
America
ATSR
AVHRR
TRMM
GLOBSCAR
GBA2000
Indonesia
The ATSR night time restrictions show a seasonal cycle
that is consistent with the other proxies