Picture: METEOSAT Oct 2000 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

Outstanding scientific issue in the Tropics GOME Seasonal Tropospheric O 3 Columns 2000 DJF MAM JJA SON Topic: O 3 maximum zonal wave-one (from Fishman et al. 1987… to Wang et al 2006) Scientific interest:  year-round pattern observed since the 80’s.  Situated in MT-UT  O 3 critical for radiative effect  Key role on the oxidizing power of the atmosphere  O 3 maximum attributed to various anthropogenic and natural sources + dynamics Goal: What controls O 3 maximum? (Sources / regions) data from Liu et al 2005DU

Methodology What controls the O 3 maximum? High estimation emissions uncertainty Global chemical transport model GEOS-Chem “Original” simulation 1 Constraint & Evaluation In-situ & satellite observations  Lightning: spatial distribution scaled to OTD-LIS  Soils: a posteriori inventory of NO x from GOME (Jaeglé et al., 2005)  Biomass burning: top-down constraint on NO x & VOCs from GOME 2 Quantification (sources / regions) O3 maximum 3 Constrained “standard” simulation

Space-based constraint on emissions NO h O3O3 NO 2 HNO 3 Lifetime hours VOC OH HCHO h hours CO hours PBL NO x VOC Free Troposphere NO NO 2 O 3, HO 2 hv HNO 3 NOx lifetime ~ week O3O3 lifetime ~ month O3O3 lifetime ~ days Tropospheric NO 2 column ~ E NOx Tropospheric HCHO column ~ E VOC GOME: 320x40 km 2 OTD-LIS Lightning flash rates

Effect of satellite constraint in simulated tropospheric column O3 Δ Tropospheric O 3 Columns “constrained” – “original ” simulations DJF MAM JJA SON ΔDU  Large influence from lightning and biomass burning constraint

Space-based constraint on lightning NO x emissions OTD-LIS flashes ( )  local seasonal rescaling of lightning emissions -Regional differences / oceanic emissions -Same intensity: 5 Tg N yr molec N cm -2 s -1 Original constrained with OTD/LIS Modeled lightning NO x emissions (DJF)

In-situ O 3, data used to evaluate the simulation 1.MOZAIC airborne program ( Marenco et al., 1998; Thouret et al ) : landing and taking off phase 2.SHADOZ ozone sonde network ( Thompson et al., 2003a; 2003b ) : More than 9000 vertical profiles of O 3 over the Tropics 30°N-30 ° S

Highlights of simulation evaluation: sensitivity to lightning 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/yr gives overall agreement. In-situ constrained

GOMEModel originalModel constrained Better agreement during biomass burning season molec cm -2 Better spatial correlations between GOME and model NO 2 columns R 2 > 0.86 Space-based constraint on biomass burning emissions GOME NO 2  regional top-down constraint of biomass burning NO x emissions data from Martin et al Tropics: 4.8TgN/yr  5.8TgN/yr DJF MAM JJA SON

Better spatial correlations between GOME and model HCHO columns R 2 > 0.7 Space-based constraint on biomass burning emissions data from Chance et al Better agreement during biomass burning season GOME HCHO  top-down constraint of biomass burning VOC emissions HCHO and alkenes emissions increased x 2 GOMEGEOS-Chem constrainedGEOS-Chem original

Highlights of simulation evaluation: sensitivity to biomass burning Top-down improves lower tropospheric O 3 from 5-20 ppbv during biomass burning season Main influence over Africa DJF-JJA; India MAM

Use of constrained simulation  Quantify (sources/regions) influencing O 3 maximum What controls the O3 maximum? O 3 maximum ?

O3 budget / Sensitivity to sources Sensitivity to decreasing NOx emissions by 1% and 100% for each source ΔDU -Lightning  downwind; largest influence over the Tropics & South Atlantic >36%>7%>9% DJF MAM JJA SON -Surface sources  local; half of the lightning NO x influence (but similar source strength) -Lightning Ozone Production Efficiency = 3 times OPE of each surface source -Tropical background 30%

O3 budget Sensitivity to regions ΔDU Sensitivity to decreasing NO x emissions by 1% over regions >20%>15%>6% DJF MAM JJA SON

The zonal-wave one Vertical-zonal seasonal cross section of O 3 and O 3 flux DJFMAM JJA SON subsidenceAfricaS. America

Dynamical description / annual mean O3O3 ppb NO x ppb 3/O 3 buildup during transport and subsidence over South Atlantic high area Zonal transport 1/Surface emissions of O 3 precursors S. Am.Africa 2/Injection of NOx into the MT-UT with lightning emissions and uplift into ITCZ Modeled SHADOZ+ MOZAIC O 3 (ppbv) 4/ Meridional transport Meridional transport AFRICAATLANTIC SN O 3 (ppbv)

Conclusions 1/ Spatial distribution of lightning scaled to reproduce OTD-LIS seasonal mean  Improve MT-UT O 3 by 5 to 15 ppbv 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 Lightning source of 5 Tg±2Tg best reproduces versus in-situ MOZAIC & SHADOZ >6% >20% > 21%> 36% EAST AFRICA South America O 3 maximum is driven by convergence and sustained largely by lightning NO x emissions, which present larger OPE >15% Surface NOx sourcesSTE ~ 6% (500 Tg/yr)

Picture: METEOSAT Oct 2000 Thanks for attention!

Comparison of convective schemes ITCZ O 3 min/ CO max/ RH max GEOS-3 presents weak convective outflow GEOS-4 low clouds altitude & optical thickness Weak incidence over the Atlantic ITCZ Flight altitude mean over Africa, hPa, JJA season CORH O3O3

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

Space-based constraint on emissions 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 molec N.cm -2.s -1 Seasonal NO x biomass burning emissions (DJF) OriginalStandard