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Processes driving O3 within the troposphere The Tropics / The Atlantic

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Title: Processes driving O3 within the troposphere The Tropics / The Atlantic


1
Processes driving O3 within the troposphere The
Tropics / The Atlantic
  • Bastien Sauvage et al.

2
Ozone within the Tropics
O3 maximum zonal wave-one 40W-60E
MOZAICSHADOZ (1994-2004) zonal cross section O3
(ppbv)
TOMS tropospheric O3 columns (1997)
SON
Pressure (hPa)
W
E
longitude
Sauvage et al., JGR 2006
Martin et al., JGR 2002
  • Observed since the 80s Logan and Kirchhoff,
    1986 Fishman et al. 1987
  • In the middle upper troposphere ? maximum
    radiative effect (de Forster, 1997)
  • Key role on the oxidizing power of the atmosphere
    (Jacob et al, JGR 1996)
  • ? Attributed to various anthropogenic and natural
    sources from Fishman et al. 1987 Thompson et al.
    20002003 to Wang et al 2006

Goal Quantify what controls tropical O3 / in the
Atlantic?
3
(1) Overview Tools Tropospheric ozone
chemistry The Tropics chemical and dynamical
context (2) Methodology (3) Model
evaluation -Chemistry Constraint on lightning
and fire emissions -Dynamic (4) What controls the
zonal wave one? (5) Conclusions
4
Coupled approach observations/model
Satellite instruments
In Situ
Models
MOZAIC programme (Marenco et al., 1998
Volz-Thomas 2005) 1994-present
GOME SCIAMACHY OMI Spectrometers backscattered
solar radiations O3/ NO2/ HCHO OTD/LIS Lightning
flashes
LAGRANTO FLEXPART Méso-NH GEOS-Chem
Automatic measurements O3 , H2O CO , NOy High
temporal and spatial resolution and
distribution overall O3 precision 2 ppbv.
ACE Fourier Transform Spectrometer/ Solar
occultation
26000 Flights
5
Issues the Tropics (chemistry)
STE
hv
hv,H2O
Nitrogen oxides (NOx) CO, Hydrocarbons
Ozone (O3)
Hydroxyl (OH)
Fires
Biosphere
Anthropogenic activity
O3 production primarily NOx limited
Tropics -Higher tropospheric reservoir -Photoche
mical activity exacerbated (High UV and relative
humidity)
  • -Numerous O3 precursor sources
  • Spatial distribution known
  • Uncertainty on emissions magnitude

6
Issues the Tropics (sources) 1/ Biogenic emissions
Soils
Natural source NOx (pulses) through bacterial
nitrification Monsoon season Africa North
India May-June
70 soil NOx emitted within the Tropics Global
production 4-21 Tg N/yr uncertain!
7
Issues the Tropics (sources) 2/ lightning
emissions (Li-NOx)
Lightning density (1995-2004) OTD LIS
DJF
Emissions NOx (NOgt75)
JJA
Flash number km-2 min-1
Lightning activity mainly located within the
Tropics (65 of Li-NOx) !
Global production 1-13 Tg N/yr uncertain!
8
Issues the Tropics (sources) 3/ biomass burning
emissions
fires 2005 (MODIS)
50
100
150
0
Source of NOx, VOCs
NOx 70 within the Tropics Global production
3-13 Tg N/yr uncertain!
9
Issues the Tropics (sources) 3/ biomass burning
emissions seasonal variations
Active fires AVHRR
10
Issues Dynamical context
Streamlines 850hPa (ECMWF)
EQUATORIAL Africa and the Atlantic
Saharan High
Harmattan
Harmattan
East African Low level jet
Monsoon
Trades
Trades
St. Elena H
St. Elena H
JULY
JANUARY
Fires
Inter tropical front (ITF)
11
Issues Dynamical context
Meridional cross section
Tropical Easterly Jet
100hPa
ITCZ
N Hadley
S Hadley
600hPa
African EJ
NE HARMATTAN
SW monsoon
Sahara
ITF
30N
10N
20N
EQUATOR
5S
Schematic circulation over West Africa monsoon
season (JJA)
12
Issues Role of dynamic
LAGOS (Gulf of Guinea ) / DJF MOZAIC data
(1994-2005)
Pressure (hPa)
Sauvage et al., ACP, 2005
13
Issues Role of the dynamic
Equivalent potential temperature (K)
Meridional baroclinic cells
(surface gradients role)
Altitude (km)
Meridional circulation
T /H-
T- /H
?e
Sauvage et al., ACP, to be submitted
Méso-NH simulation
latitude
  • Lower tropospheric transport (trades, jets)?
    affects O3 distribution (link between emissions
    and in situ measurements)

?Transport and creation of high O3 and CO
concentrations from fires ( gt70 ppbv 500 ppbv
in monthly mean!)
14
Issues Role of the dynamic
O3 meridional gradients MOZAIC transects
300-180hPa
  • Convection ITCZ
  • ? Affects O3 distribution

Hadley cells
Latitude
Europe
South Africa
Sauvage et al GRL, in press
Hadley cells role ? redistribution fires Li-NOx
emissions
  • Convection role in the Tropics
  • 1/ Efficient and rapid vertical
  • redistribution of precursors and species in the
    UT (longer lifetime)
  • 2/ Global redistribution
  • 3/ HOx impact? UT reactivity

15
Issues summary
1/ Important O3 precursor emissions in the
Tropics ? But uncertain (intensity /
processes) 2/ Importance of dynamics in the
Tropics ? Lower troposphere (LT) and upper
troposphere (UT) transport 3/ Importance of
tropospheric ozone in the Tropics ? High O3 and
precursors concentrations in the LT and UT
Necessity to evaluate emissions and dynamic to
better understand what controls O3 distributions
16
(1) Overview Tropospheric ozone chemistry
Tropics chemical and dynamical context (2)
Methodology (3) Model evaluation -Chemistry
Constraint on lightning and fire
emissions -Dynamic (4) What controls the zonal
wave one? (5) Conclusions
17
Methodology
CTM (GEOS-Chem) Original version
Understand O3 In the Tropics
1
2
Constraint and modifications (in situ and
satellites)
  • Soils NOx  a posteriori inventory GOME (Jaeglé
    et al., Farad., 2005)

? Lightning local redistribution OTD-LIS
? Fires top-down inventory NOx VOCs / GOME
Quantification (sources / regions) O3 maximum
3
4
Evaluation O3/RH/CO
Constrained Model
18
(1) Overview Tropospheric ozone chemistry
Tropics chemical and dynamical context (2)
Methodology (3) Model evaluation -Chemistry
Constraint on lightning and fire
emissions -Dynamic (4) What controls the zonal
wave one? (5) Conclusions
19
Lightning NOx (Li-NOx) constraint Ozone
sensitivity
20
Space-based constraint on Li-NOx spatial
distribution
GEOS-Chem simulations exhibited different spatial
distribution of lightning compared to satellite
Calculation of rescaling factor (R) OTD-LIS
climatologies (1995-2004) ? spatial lightning
redistribution (local approach) for simulated
convective events
-Factors are applied each month for the given
season to retain monthly variation -If there is
no deep convection in GEOS-Chem, no flashes, R
1 -No large episodic injection were apparent as
convection as low temporal variability
21
Space-based constraint on Li-NOx spatial
distribution
Modified version OTD/LIS
LiNOx simulated
original version
DJF
DJF
JJA
JJA
NOx emissions (109 molec N/cm2/s)
-Important regional differences (seasonal
latitudinal variation allowed) / Higher oceanic
emissions -Same intensity 6 Tg N yr-1
22
In situ data used to evaluate simulation
(O3/CO/RH)
1.MOZAIC programme 1994-2005
2.SHADOZ ozone sonde network (Thompson et al.,
2003ab) 1998-2004
MOZAIC SHADOZ sites used for model evaluation
gt 9000 O3 / RH vertical profiles within the
Tropics (30N-30S)
23
O3 sensitivity to Lightning NOx spatial
distribution
Snapshot of the model evaluation
Original Modified In situ
Pressure (hPa)
Pressure (hPa)
O3 (ppbv)
O3 (ppbv)
-O3 highly sensitive in the MT-UT -O3 simulations
improved by 5-15 ppbv / In situ -Main influence
near subsidence areas South America Middle
East Atlantic
24
O3 sensitivity to LiNOx intensity 4 TgN/yr 6
TgN/yr 8 TgN/yr
Pressure (hPa)
Pressure (hPa)
O3 (ppbv)
Evaluation for the Tropics 8Tg N/yr ? O3 over
estimation 4Tg N/yr ? O3 under estimation
62Tg N/yr ? general agreement (including
ICARTT results Hudman et al 2006)
O3 (ppbv)
Sauvage et al., ACPD 2006
25
O3 sensitivity to LiNOx intensity using different
satellite observations
NO2 SCIAMACHY
6TgN/yr in agreement with model/satellite study
NO2/HNO3/O3 Martin et al., JGR, in press ? 62Tg
N/yr
O3 OMI
Annual meridional mean HNO3 (200-350hPa)
HNO3 (ACE)
Model 6TgN/yr 4TgN/yr
8TgN/yr
HNO3 (pptv)
longitude
Simulated HNO3 / LiNOx between 4 and 8TgN/yr
No lightning
No wave-one pattern
W
E
26
Biomass burning emissions constraint O3
sensitivity
Savanna fires (SAFARI 2000)
27
How to use remote-sensed data to constrain
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 hours
Lifetime hours
Emissions NOx
VOC
28
Space-based constraint on biomass burning
emissions NOx
NOx emissions / Tropics 4.8TgN/yr ? 5.8TgN/yr
GOME NO2
original model NO2
Constrained model NO2
DJF
MAM
JJA
SON
1015 molec cm-2
Better agreement during biomass burning season
Better spatial correlations between GOME and
model NO2 columns R2 gt 0.86
29
Space-based constraint on biomass burning
emissions VOC
GEOS-Chem tropospheric HCHO presented systematic
bias with GOME over biomass burning region
Tentatively attribute bias to HCHO and alkenes
biomass burning emissions
1-Evidence of higher reactive VOC EF from
literature
GEOS-Chem original (Andreae and Merlet 2001) Andreae compilation (2005) (Bertschi et al. 2003Yokelson et al., 2003)
Alkenes 0.3g/kg 1.4?0.6 g/kg
HCHO 0.36g/kg 0.7?0.4g/kg
30
Space-based constraint on biomass burning
emissions VOC
2-Bias not corrected using MEGAN
Seasonal HCHO tropospheric columns (1016
molecules/cm2)
GEOS-Chem with MEGAN 2000
GOME 2000
? Use of GOME HCHO to constrain VOC over biomass
burning regions
31
Space-based constraint on biomass burning
emissions VOC
GOME HCHO ? fires VOC emissions HCHO and
alkenes increased x 2
GOME HCHO
Contrained model HCHO
original model HCHO
Better agreement during biomass burning season
Better spatial correlations between GOME and
model HCHO columns R2gt 0.7
32
O3 sensitivity to fire emissions (NOx and VOCs)
Lagos Nigeria DJF
Abidjan Ivory Coast DJF
? Original ? Constraint ? In Situ
Pressure (hPa)
Pressure (hPa)
O3 (ppbv)
Congo-Brazzaville JJA
Top-down improves lower tropospheric O3 from 5-20
ppbv during biomass burning season Main influence
over Africa DJF-JJA India MAM
Pressure (hPa)
Model problems in reproducing meso scale
processes (monsoon flow)
33
Dynamic sensitivity
34
Convection effect GEOS3/GEOS4
Convection affects vertical distribution of
species, especially in the outflow
Detrainment and entrainment (upwarddownward) /
cloudy column 20S-20N
entrainment
detrainment
GEOS3 GEOS4
1.Convection Weak divergence -
2.Cloud Top Height -
3.Cloud Optical Depth -
Deep outflow layer GEOS4
Liu et al 2006 Wu et al2006
Folkins et al., 2006
35
Role of convection chemical species as
convection tracers
36
GEOS3 vs GEOS4
Pressure (hPa)
In situ GEOS 4 GEOS 3
Ozone (ppbv)
RH ()
  • GEOS3 weak deep outflow
  • Convection affects ozone but also
  • Li-NOx does (vertical placement) and radiative
    effect (photolysis frequencies)

37
3. What controls O3 maximum in the Atlantic?
O3 maximum
?
38
Atlantic O3 budget/ Sensitivity to sources
O3 sensitivity to NOx emissions? NOx decreased
by 1 for each source (non linear chemistry)
?O3 tropospheric
4TgN/yr
3TgN/yr
5TgN/yr
DJF
SON
?DU
Lightning ? main tropical and Atlantic influence
/ Surface sources ? local influence
Influence on the Atlantic (no emissions) LiNOx
gt36 tropical Atlantic O3 Soils gt7 Fires gt 9
half of lightning (despite similar NOx
intensity) Background 30
Lightning Ozone Production Efficiency (OPE) 3
time each surface source OPE
39
Atlantic O3 budget / sensitivity to regions
Sensitivity to decreasing NOx emissions by 1
over regions
?O3 tropospheric
gt20
gt15
gt6
DJF
MAM
JJA
SON
?DU
40
zonal-wave one
Zonal/Vertical cross-section / O3 (ppbv) O3 flux
(kg/s)
DJF
MAM
JJA
SON
41
Dynamic of the O3 maximum
Zonal transport
Model 2000
O3
ppb
42
Oxidizing capacity of the tropical troposphere
Tropical OH ?OHlightning ?OHsurface
Annual mean 106 molec cm-3s-1) 1.51 0.54 0.40
Spivakovsky et al. (2000) Tropical OH 1.41
106 molec cm-3s-1 (climatologies) ? Model over
estimation by 6
LiNOx dominates oxidizing capacity within the
Tropics (gt35 vs gt26 for total surface sources)
43
Conclusions processes driving the O3 max
gt 21
gt 36
NOx surface sources
STE 6
AFRICA
gt20
EAST
gt6
gt15
South America
Engine convergence subsidence Fuel in
majority Li-NOx, with higher OPE
44
Acknowledgements
Randall V. Martin, Aaron van Donkelaar, Ian
Folkins, Dalhousie University Paul I. Palmer,
Edinburgh University Kelly Chance, Xiong Liu
Harvard-Smithsonian May Fu, Shiliang Wu, Bob
Yantosca and all the GEOS-Chem community Harvard
University MOZAIC team, LA, FZJ Meinrat.O.
Andreae, MPI Dennis Boccippio, Jerry Ziemke,
NASA Anne M. Thompson, Pennsylvania
University Peter Bernath, Toronto
University Lyatt Jaeglé, Washington
University Supported by NASA atmospheric
composition program
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