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Tropospheric O 3 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. Outstanding scientific issue in the Tropics.

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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


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 80’s.

  • Situated in MT-UT O3critical for radiative effect

  • Key role on the oxidizing power of the atmosphere

  • O3 maximumattributed to various anthropogenic and natural sources + dynamics

MAM

JJA

Goal:

What controls O3 maximum?

(Sources / regions)

SON

DU

data from Liu et al 2005


Methodology

What controls

the O3 maximum?

1

Global chemical transport model

GEOS-Chem “Original” simulation

High estimation emissionsuncertainty

2

Constraint & Evaluation

In-situ & satellite observations

 Soils: a posteriori inventory of NOxfrom 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


Space-based constraint on emissions

Tropospheric NO2 column ~ ENOx

Tropospheric HCHO column ~ EVOC

GOME: 320x40 km2

OTD-LIS

Lightning flash rates

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


Effect of satellite constraint in simulated tropospheric column O3

 Large influence from lightning and biomass burning constraint

ΔTropospheric O3 Columns “constrained” – “original ”simulations

DJF

MAM

JJA

SON

ΔDU


Space-based constraint on column O3lightning NOxemissions

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


In-situ O column O33, 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 30°N-30°S


Highlights of simulation evaluation: sensitivity to column O3lightning

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;

5±2Tg N/yrgives overall agreement.


Space-based constraint on column O3biomass burning emissions

GOME NO2regional top-down constraint of biomass burning NOxemissions

Tropics: 4.8TgN/yr  5.8TgN/yr

GOME

Model constrained

Model original

DJF

MAM

JJA

SON

data from Martin et al. 2002

1015 molec cm-2

Better agreement during biomass burning season

Better spatial correlations between

GOME and model NO2 columns R2 > 0.86


Space-based constraint on column O3biomass burning emissions

GOME HCHO top-down constraint of biomass burning VOCemissions

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 R2> 0.7

Better agreement during biomass burning season


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


What controls the O3 maximum? burning

Use of constrained simulation  Quantify (sources/regions) influencing O3 maximum

O3 maximum

?


O3 budget / Sensitivity to sources burning

Sensitivity to decreasing NOx emissions by 1% and 100% for each source

>36%

>7%

>9%

DJF

MAM

JJA

SON

ΔDU

-Lightning downwind;largest influenceover 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%


O3 budget Sensitivity to regions burning

Sensitivity to decreasing NOx emissions by 1% over regions

>20%

>15%

>6%

DJF

MAM

JJA

SON

ΔDU


The zonal-wave one burning

Vertical-zonal seasonal cross section of O3 and O3 flux

S. America

DJF

Africa

MAM

subsidence

JJA

SON


Dynamical description / annual mean burning

Meridional transport

SHADOZ+ MOZAIC

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/ Meridional transport

ATLANTIC

AFRICA

S

N

O3 (ppbv)

O3 (ppbv)

Zonal transport

Modeled

O3

ppb


Conclusions burning

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 Tg±2Tg best reproducesversusin-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

Surface NOx sources

> 21%

> 36%

STE ~ 6%

(500 Tg/yr)

AFRICA

>20%

EAST

South America

>6%

>15%

O3 maximum is driven by convergence and sustained largely by lightning NOx emissions, which present larger OPE


Thanks for attention! burning

Picture: METEOSAT Oct 2000


Comparison of convective schemes burning

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


CO & Relative humidity evaluation burning

CO lower estimated in LT / CO; emissions increased by 2  weak or negative impact on modeled versus in-situ


Space-based constraint on emissions burning

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.


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