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Processes driving O 3 within the troposphere The Tropics / The Atlantic. Bastien Sauvage et al. Ozone within the Tropics. O 3 maximum “zonal wave-one” 40W-60E. MOZAIC+SHADOZ (1994-2004) zonal cross section O3 (ppbv). TOMS tropospheric O 3 columns (1997). SON. Pressure (hPa). W. E.

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slide2

Ozone within the Tropics

O3 maximum “zonal wave-one” 40W-60E

MOZAIC+SHADOZ (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 80’s 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 sourcesfrom Fishman et al. 1987… Thompson et al. 2000;2003… to Wang et al 2006

Goal: Quantify what controls tropical O3 / in the Atlantic?

slide3

(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

slide4

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 , NOyHigh temporal and spatial resolution and distribution

overall O3 precision ± [2 ppbv].

ACE

Fourier Transform

Spectrometer/

Solar occultation

+26000 Flights

slide5

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

-Photochemical activity exacerbated

(High UV and relative humidity)

-Numerous O3 precursor sources

Spatialdistribution ~known

Uncertainty on emission’s magnitude

slide6

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!

slide7

Issues: the Tropics (sources)

2/ lightning emissions (Li-NOx)

Lightning density (1995-2004) OTD & LIS

DJF

Emissions:

NOx (NO>75%)

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!

slide8

Issues: the Tropics (sources)

3/ biomass burning emissions

#fires 2005 (MODIS)

0

50

100

150

Source of NOx, VOCs …

NOx: ~70% within the Tropics

Global production : 3-13 Tg N/yr …uncertain!

slide9

Issues: the Tropics (sources)

3/ biomass burning emissions: seasonal variations

Active fires AVHRR

slide10

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)

slide11

Issues: Dynamical context

Meridional cross section

Tropical Easterly Jet

100hPa

ITCZ

NHadley

S Hadley

600hPa

African EJ

NE HARMATTAN

SW monsoon

Sahara

ITF

30°N

10°N

20°N

EQUATOR

5°S

Schematic circulation over West Africa

monsoon season (JJA)

slide12

Issues: Role of dynamic

u<0, v=0/AEJ

u,v <0/Harmattan

LAGOS

LAGOS

•fire pixels (ATSR)

•fire pixels (ATSR)

Pressure (hPa)

Pressure (hPa)

600

650

700

750

800

850

900

950

600

650

700

750

800

850

900

950

LAGOS(Gulf of Guinea ) / DJF

MOZAIC data (1994-2005)

Pressure (hPa)

Sauvage et al., ACP, 2005

slide13

Issues: Role of the dynamic

Equivalent potential temperature (K)

Meridional baroclinic cells

(surface gradients role)

Altitude (km)

Meridional

circulation

T- /H+

T+ /H-

e

Méso-NH simulation

Sauvage et al., ACP, to

be submitted

latitude

  • Lower tropospheric transport (trades, jets) affects O3 distribution (link between emissions and in situ measurements)

Transport and creation of high O3 and COconcentrationsfrom fires

( >70 ppbv & 500 ppbv in monthly mean!)

slide14

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

slide15

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

slide16

(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

slide17

Methodology

CTM (GEOS-Chem)

Original version

Understand O3

In the Tropics

1

2

Constraint and modifications(in situ and satellites)

  • Soils: NOxa posteriori inventory GOME(Jaeglé et al., Farad., 2005)

Lightning: local redistribution OTD-LIS

Fires: top-down inventoryNOx & VOCs / GOME

Quantification (sources / regions)

O3 maximum

3

4

Evaluation

O3/RH/CO

Constrained Model

slide18

(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

slide20

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

slide21

Space-based constraint on Li-NOx spatial distribution

LiNOx simulated

Modified version OTD/LIS

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

slide22

In situ data used to evaluate simulation

(O3/CO/RH)

1.MOZAIC programme 1994-2005

2.SHADOZ ozone sonde network (Thompson et al., 2003a;b): 1998-2004

MOZAIC & SHADOZ sites used for model evaluation

> 9000 O3 / RH vertical profiles within the Tropics (30°N-30°S)

slide23

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

slide24

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  O3under estimation

6±2Tg N/yrgeneral agreement

(including ICARTT results Hudman et al; 2006)

O3 (ppbv)

Sauvage et al., ACPD 2006

slide25

O3 sensitivity to LiNOx intensity using different satellite observations

NO2 SCIAMACHY

6TgN/yr in agreement with model/satellite studyNO2/HNO3/O3Martin et al., JGR, in press6±2Tg 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

slide26

Biomass burning emissions constraint

O3 sensitivity

Savanna fires (SAFARI 2000)

slide27

How to use remote-sensed data to constrain emissions?

Tropospheric NO2 column ~ ENOx

Tropospheric HCHO column ~ EVOC

GOME: 320x40 km2

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

slide28

Space-based constraint on biomass burning emissions:

NOx

NOx emissions / Tropics: 4.8TgN/yr  5.8TgN/yr

GOME NO2

Constrained model NO2

original model NO2

DJF

MAM

JJA

SON

1015 molec cm-2

Better spatial correlations between

GOME and model NO2 columns R2 > 0.86

Better agreement during biomass burning season

slide29

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

slide30

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

slide31

Space-based constraint on biomass burning emissions:

VOC

GOME HCHO fires VOCemissions : 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 R2> 0.7

slide32

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)

slide34

Convection effect GEOS3/GEOS4

Convection affects vertical distribution of species, especially in the outflow

Detrainment and entrainment

(upward+downward) / cloudy column 20S-20N

entrainment

detrainment

Deep outflow

layer GEOS4

Liu et al; 2006; Wu et al;2006;

Folkins et al., 2006

slide35

Role of convection: chemical species as convection tracers

MOZAIC

GEOS4

GEOS3

RH (%)

CO (ppbv)

MOZAIC transect

Further

comparison

with daily flights

Latitude (25S-25N)

Latitude (25S-25N)

ITCZ

Convection tracers (ITCZ)

O3- / RH + / CO +

O3 (ppbv)

  • GEOS3 weak deep outflow / Weak convective detrainment

Latitude (25S-25N)

slide36

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)

slide38

Atlantic O3 budget/ Sensitivity to sources

O3 sensitivity to NOx emissions NOxdecreased by 1% for each source

(non linear chemistry)

ΔO3 tropospheric

4TgN/yr

3TgN/yr

5TgN/yr

DJF

SON

ΔDU

Lightningmain tropical and Atlantic influence / Surface sources local influence

Influence on the Atlantic (no emissions):

LiNOx: >36% tropicalAtlanticO3

Soils >7%; Fires > 9% …half of lightning

(despite similar NOx intensity)

’Background’ 30%

Lightning Ozone Production Efficiency (OPE)= 3 time each surface source OPE

slide39

Atlantic O3 budget / sensitivity to regions

Sensitivity to decreasing NOx emissions by 1% over regions

ΔO3 tropospheric

>20%

>15%

>6%

DJF

MAM

JJA

SON

ΔDU

slide40

“zonal-wave one”

South Am.

Africa

subsidence

Zonal/Vertical cross-section / O3 (ppbv) O3 flux (kg/s)

DJF

MAM

JJA

SON

slide41

Dynamic of the O3 maximum

Meridional Transport

SHADOZ+ MOZAIC

1994-2005

S. Am.

Africa

NOx

ppb

1/Surface emissions of O3 precursors

2/Injection of NOx into the MT-UT with lightning emissions and uplift into ITCZ

3/O3 buildup during transport and subsidence over South Atlantic high area

4/ zonal transport

ATLANTIC

AFRICA

S

N

O3 (ppbv)

O3 (ppbv)

Zonal transport

Model

2000

O3

ppb

slide42

Oxidizing capacity of the tropical troposphere

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

(>35% vs >26% for total surface sources)

slide43

Conclusions: processes driving the O3 max

NOx surface sources

> 21%

> 36%

STE ~ 6%

AFRICA

>20%

EAST

>6%

>15%

South America

Engine: convergence & subsidence

Fuel: in majority Li-NOx, with higher OPE

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

Acknowledgements :
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