Picture: METEOSAT Oct 2000

1
Tropospheric O3 budget of the South Atlantic
region
B. Sauvage, R. V. Martin, A. van Donkelaar, I.
Folkins, X.Liu, P. Palmer, V. Thouret , A. M.
Thompson, P. Bernath K. Chance
Picture METEOSAT Oct 2000
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Outstanding scientific issue in the Tropics
Topic O3 maximum zonal wave-one (from Fishman et
al. 1987 to Wang et al 2006)
GOME Seasonal Tropospheric O3 Columns 2000
DJF

• Scientific interest
• ? year-round pattern observed since the 80s.
• Situated in MT-UT ? O3 critical for radiative
  effect
• Key role on the oxidizing power of the atmosphere
  
• O3 maximum attributed to various anthropogenic
  and natural sources dynamics

MAM
JJA
Goal What controls O3 maximum? (Sources /
regions)
SON
data from Liu et al 2005
DU
3
Methodology
What controls the O3 maximum?
1
Global chemical transport model GEOS-Chem
Original simulation
High estimation emissions uncertainty
2
Constraint Evaluation In-situ satellite
observations
? Soils a posteriori inventory of NOx from GOME
(Jaeglé et al., 2005)
? Biomass burning top-down constraint on NOx
VOCs from GOME
? Lightning spatial distribution scaled to
OTD-LIS
Quantification (sources / regions) O3 maximum
3
Constrained standard simulation
4
Space-based constraint on emissions
hv
O3
NO
NO2
lifetime month
O3, HO2
NOx lifetime week
Free Troposphere
HNO3
h?
PBL
h?
NO2
HCHO
CO
NO
OH
hours
hours
O3
O3
VOC
HNO3
lifetime days
Lifetime hours
NOx
VOC
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Effect of satellite constraint in simulated
tropospheric column O3
? Large influence from lightning and biomass
burning constraint
? Tropospheric O3 Columns constrained
original simulations
DJF
MAM
JJA
SON
?DU
6
Space-based constraint on lightning NOx emissions
OTD-LIS flashes (1995-2004) ? local seasonal
rescaling of lightning emissions
Modeled lightning NOx emissions (DJF)
Original
constrained with OTD/LIS
109 molec N cm-2 s-1
-Regional differences / oceanic emissions -Same
intensity 5 Tg N yr-1
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In-situ O3, data used to evaluate the simulation
1.MOZAIC airborne program (Marenco et al., 1998
Thouret et al. 1998) 1994-2004 landing and
taking off phase
2.SHADOZ ozone sonde network (Thompson et al.,
2003a 2003b) 1998-2004
More than 9000 vertical profiles of O3 over the
Tropics 30N-30S
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Highlights of simulation evaluation sensitivity
to lightning
constrained
In-situ
Rescaling improve middle-upper tropospheric O3
from 5-15 ppbv Main influence over subsident
zone South America Middle East
East Sensitivity to lightning intensity 7Tg
N/yr too high 3Tg N/yr too low 52Tg N/yr
gives overall agreement.
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Space-based constraint on biomass burning
emissions
GOME NO2 ? regional top-down constraint of
biomass burning NOx emissions
Tropics 4.8TgN/yr ? 5.8TgN/yr
GOME
Model original
Model constrained
DJF
MAM
JJA
SON
1015 molec cm-2
data from Martin et al. 2002
Better agreement during biomass burning season
Better spatial correlations between GOME and
model NO2 columns R2 gt 0.86
10
Space-based constraint on biomass burning
emissions
GOME HCHO ? top-down constraint of biomass
burning VOC emissions
HCHO and alkenes emissions increased x 2
GOME
GEOS-Chem constrained
GEOS-Chem original
data from Chance et al. 2000
Better spatial correlations between GOME and
model HCHO columns R2gt 0.7
Better agreement during biomass burning season
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Highlights of simulation evaluation sensitivity
to biomass burning
Top-down improves lower tropospheric O3 from 5-20
ppbv during biomass burning season Main
influence over Africa DJF-JJA India MAM
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What controls the O3 maximum?
Use of constrained simulation ? Quantify
(sources/regions) influencing O3 maximum
O3 maximum
?
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O3 budget / Sensitivity to sources
Sensitivity to decreasing NOx emissions by 1 and
100 for each source
gt36
gt7
gt9
DJF
MAM
JJA
SON
?DU
-Lightning ? downwind largest influence over the
Tropics South Atlantic
-Surface sources ? local half of the lightning
NOx influence (but similar source strength)
-Lightning Ozone Production Efficiency 3 times
OPE of each surface source
-Tropical background 30
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O3 budget Sensitivity to regions
Sensitivity to decreasing NOx emissions by 1
over regions
gt20
gt15
gt6
DJF
MAM
JJA
SON
?DU
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The zonal-wave one
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Dynamical description / annual mean
Zonal transport
Modeled
O3
ppb
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Conclusions
1/ Spatial distribution of lightning scaled to
reproduce OTD-LIS seasonal mean ? Improve MT-UT
O3 by 5 to 15 ppbv
Lightning source of 5 Tg2Tg best reproduces
versus in-situ MOZAIC SHADOZ
2/ Top-down constraint on emission inventories of
NOx from soil and biomass burning, of VOCs from
biomass burning improve LT O3 by 5 to 20 ppbv
gt 21
gt 36
Surface NOx sources
STE 6
(500 Tg/yr)
AFRICA
gt20
EAST
South America
gt6
gt15
O3 maximum is driven by convergence and
sustained largely by lightning NOx emissions,
which present larger OPE
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Thanks for attention!
Picture METEOSAT Oct 2000
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Comparison of convective schemes
Flight altitude mean over Africa, 300-200hPa, JJA
season
CO
RH
ITCZ
GEOS-3 presents weak convective outflow GEOS-4
low clouds altitude optical thickness
ITCZ
O3 min/ CO max/ RH max
Weak incidence over the Atlantic
O3
ITCZ
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CO Relative humidity evaluation
CO lower estimated in LT / CO emissions
increased by 2 ? weak or negative impact on
modeled versus in-situ
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(No Transcript)
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Space-based constraint on emissions
Seasonal NOx biomass burning emissions (DJF)
Original
Standard
109 molec N.cm-2.s-1
Different intensity of NOx emissions Biomass
burning 4.8TgN/yr ? 5.8TgN/yr / Soils 3.5TgN/yr
? 4.5TgN/yr (Tropics). Larger influence over
Africa and India.