Processes driving O 3 within the troposphere The Tropics / The Atlantic Bastien Sauvage et al. MOZAIC+SHADOZ ( ) zonal cross section O3 (ppbv) Ozone within the Tropics Martin et al., JGR 2002 O 3 maximum zonal wave-one 40W-60E Observed since the 80s Logan and Kirchhoff, 1986; Fishman et al 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. 2000;2003 to Wang et al 2006 Pressure (hPa) Sauvage et al., JGR 2006 longitude Goal: Quantify what controls tropical O 3 / in the Atlantic? SON TOMS tropospheric O 3 columns (1997) WE (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 Coupled approach observations/model MOZAIC programme ( Marenco et al., 1998 Volz-Thomas 2005 ) : 1994-present Automatic measurements O 3, H 2 O + CO, NO y High temporal and spatial resolution and distribution overall O 3 precision [2 ppbv] Flights In Situ Models Satellite instruments GOME SCIAMACHY OMI Spectrometers backscattered solar radiations O 3 / NO 2 / HCHO OTD/LIS Lightning flashes LAGRANTO FLEXPART Mso-NHGEOS-Chem ACE Fourier Transform Spectrometer/ Solar occultation FiresBiosphereAnthropogenic activity Nitrogen oxides (NO x ) CO, Hydrocarbons Ozone (O 3 ) Hydroxyl (OH) hvhv,H 2 O O 3 production primarily NO x limited Issues: the Tropics (chemistry) STE Tropics: -Higher tropospheric reservoir -Photochemical activity exacerbated (High UV and relative humidity) -Numerous O 3 precursor sources Spatial distribution ~known Uncertainty on emissions magnitude Soils Natural source : NO x (pulses) through bacterial nitrification Monsoon season: Africa; North India; May-June ~ 70% soil NO x emitted within the Tropics Global production : 4-21 Tg N/yr uncertain! Issues the Tropics (sources) 1/ Biogenic emissions Emissions: NOx (NO>75%) Lightning density ( ) OTD & LIS Flash number km -2 min -1 DJF JJA Lightning activity mainly located within the Tropics (~65% of Li- NOx) ! Global production : 1-13 Tg N/yr uncertain! Issues: the Tropics (sources) 2/ lightning emissions (Li-NOx) Source of NO x, VOCs #fires 2005 (MODIS) NOx: ~70% within the Tropics Global production : 3-13 Tg N/yr uncertain! Issues: the Tropics (sources) 3/ biomass burning emissions Issues: the Tropics (sources) 3/ biomass burning emissions: seasonal variations Active fires AVHRR St. Elena H Trades Monsoon East African Low level jet Harmattan Streamlines 850hPa (ECMWF) EQUATORIAL Africa and the Atlantic JANUARY JULY Harmattan St. Elena H Saharan High Trades Issues: Dynamical context Inter tropical front (ITF) Fires Issues: Dynamical context African EJ Tropical Easterly Jet N Hadley S Hadley SW monsoon NE HARMATTAN EQUATOR 10N20N 30N 600hPa 100hPa Schematic circulation over West Africa monsoon season (JJA) ITCZ ITF Sahara Meridional cross section 5S LAGOS / DJF LAGOS (Gulf of Guinea ) / DJF MOZAIC ( ) MOZAIC data ( ) Pressure (hPa) u,v 9000 O 3 / RH vertical profiles within the Tropics (30N-30 S) O3 sensitivity to Lightning NOx spatial distribution -O 3 highly sensitive in the MT-UT -O 3 simulations improved by 5-15 ppbv / In situ -Main influence near subsidence areas: South America; Middle East; Atlantic Pressure (hPa) O 3 (ppbv) Original Modified In situ Snapshot of the model evaluation O3 sensitivity to LiNOx intensity 4 TgN/yr; 6 TgN/yr; 8 TgN/yr Evaluation for the Tropics 8Tg N/yr O 3 over estimation 4Tg N/yr O 3 under estimation 62Tg N/yr general agreement (including ICARTT results Hudman et al; 2006 ) Pressure (hPa) O 3 (ppbv) Sauvage et al., ACPD 2006 O 3 (ppbv) O 3 sensitivity to LiNO x intensity using different satellite observations 6TgN/yr in agreement with model/satellite study NO 2 /HNO 3 /O 3 Martin et al., JGR, in press 62Tg N/yr NO 2 SCIAMACHY O 3 OMI HNO 3 (ACE) HNO 3 (pptv) WE Model 6TgN/yr 4TgN/yr 8TgN/yr Annual meridional mean HNO 3 ( hPa) Simulated HNO 3 / LiNO x between 4 and 8TgN/yr longitude No lightning No wave-one pattern Biomass burning emissions constraint O 3 sensitivity Savanna fires (SAFARI 2000) How to use remote-sensed data to constrain emissions? NO h O3O3 NO 2 HNO 3 Lifetime hours VOC OH HCHO h hours CO hours PBL Emissions NO x VOC Free troposphere NO NO 2 O 3, HO 2 hv HNO 3 NOx lifetime ~ week O3O3 lifetime ~ month O3O3 lifetime ~ hours Tropospheric NO 2 column ~ E NOx Tropospheric HCHO column ~ E VOC GOME: 320x40 km 2 GOME NO 2 original model NO 2 Constrained model NO 2 Better agreement during biomass burning season molec cm -2 NO x emissions / Tropics: 4.8TgN/yr 5.8TgN/yr DJF MAM JJA SON Space-based constraint on biomass burning emissions: NO x Better spatial correlations between GOME and model NO 2 columns R 2 > 0.86 Space-based constraint on biomass burning emissions: VOC GEOS-Chem tropospheric HCHO presented systematic bias with GOME over biomass burning region GEOS-Chem original (Andreae and Merlet 2001) Andreae compilation (2005) (Bertschi et al. 2003Yokelson et al., 2003) Alkenes0.3g/kg 1.4 0.6 g/kg HCHO0.36g/kg 0.7 0.4g/kg 1-Evidence of higher reactive VOC EF from literature Tentatively attribute bias to HCHO and alkenes biomass burning emissions Seasonal HCHO tropospheric columns (10 16 molecules/cm 2 ) GOME 2000 GEOS-Chem with MEGAN Bias not corrected using MEGAN Space-based constraint on biomass burning emissions: VOC Use of GOME HCHO to constrain VOC over biomass burning regions GOME HCHO fires VOC emissions : HCHO and alkenes increased x 2 GOME HCHOContrained model HCHOoriginal model HCHO Space-based constraint on biomass burning emissions: VOC Better spatial correlations between GOME and model HCHO columns R 2 > 0.7 Better agreement during biomass burning season O3 (ppbv) Pressure (hPa) Top-down improves lower tropospheric O3 from 5-20 ppbv during biomass burning season Main influence over Africa DJF-JJA; India MAM O 3 sensitivity to fire emissions (NOx and VOCs) Original Constraint In Situ Model problems in reproducing meso scale processes (monsoon flow) Lagos Nigeria DJF Abidjan Ivory Coast DJF Congo-Brazzaville JJA Pressure (hPa) Dynamic sensitivity Convection effect GEOS3/GEOS4 GEOS3GEOS4 1.Convection Weak divergence Cloud Top Height +- 3.Cloud Optical Depth +- Folkins et al., 2006 Detrainment and entrainment (upward+downward) / cloudy column 20S-20N Deep outflow layer GEOS4 Convection affects vertical distribution of species, especially in the outflow detrainment entrainment Liu et al; 2006; Wu et al;2006; Role of convection: Role of convection: chemical species as convection tracers MOZAIC transect Latitude (25S-25N) Convection tracers (ITCZ) O 3 - / RH + / CO + GEOS3 weak deep outflow / Weak convective detrainment CO (ppbv) O3 (ppbv) RH (%) MOZAIC GEOS4 GEOS3 ITCZ Further comparison with daily flights GEOS3 vs GEOS4 GEOS3 weak deep outflow Convection affects ozone but also Li-NOx does (vertical placement) and radiative effect (photolysis frequencies) Pressure (hPa) Ozone (ppbv)RH (%) In situ GEOS 4 GEOS 3 3. What controls O3 maximum in the Atlantic? O 3 maximum ? Atlantic O 3 budget/ Sensitivity to sources O 3 sensitivity to NO x emissions NO x decreased by 1% for each source (non linear chemistry) DU Lightning main tropical and Atlantic influence / Surface sources local influence DJF Influence on the Atlantic (no emissions): LiNOx: >36% tropical Atlantic O 3 Soils >7%; Fires > 9% half of lightning (despite similar NOx intensity) Background 30% SON O 3 tropospheric Lightning Ozone Production Efficiency (OPE)= 3 time each surface source OPE 4TgN/yr3TgN/yr5TgN/yr DU >20%>15%>6% DJF MAM JJA SON O 3 tropospheric Atlantic O 3 budget / sensitivity to regions Sensitivity to decreasing NO x emissions by 1% over regions zonal-wave one zonal-wave one Zonal/Vertical cross-section / O 3 (ppbv) O 3 flux (kg/s) DJF MAM JJA SON subsidence AfricaSouth Am. Dynamic of the O 3 maximum 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 Model 2000 SHADOZ+ MOZAIC O 3 (ppbv) 4/ zonal transport Meridional Transport AFRICAATLANTIC SN O 3 (ppbv) Oxidizing capacity of the tropical troposphere Tropical OHOH lightning OH surface Annual mean 10 6 molec cm -3 s -1 ) Spivakovsky et al. (2000): Tropical OH: molec cm -3 s -1 (climatologies) Model over estimation by 6% LiNOx dominates oxidizing capacity within the Tropics (>35% vs >26% for total surface sources) EAST AFRICA South America > 21%> 36%NO x surface sourcesSTE ~ 6% Conclusions: processes driving the O 3 max Engine: convergence & subsidence Fuel: in majority Li-NO x, with higher OPE >6% >20% >15% 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 Jaegl, Washington University Supported by NASA atmospheric composition program