Tropospheric O 3 Over the Tropical Atlantic: A Satellite Perspective

1. Tropospheric O3 Over the Tropical Atlantic: A Satellite Perspective D. P. Edwards, J.-F. Lamarque, L. K. Emmons, J. C. Gille National Center for Atmospheric Research, Boulder CO, USA J. -L. Attie, J. -P. Cammas, Observatoire Midi Pyrenees, Toulouse, France A. Richter, University of Bremen, Germany J. R. Drummond, University of Toronto, Toronto ON, Canada

2. Tropospheric Chemistry and Biomass Burning • Tropical biomass burning for cultivation, deforestation, and savanna grazing, is a major forcing of tropospheric photochemistry • Large amounts of CO and CH4 are emitted by the smouldering fires • Oxidation of these gases by OH in the presence of NOx, either from biomass burning or from lightning sources, leads to high levels of O3 • Until recently, tropospheric studies have relied on field campaigns, regular groundbased and aircraft measurements, together with an important input from chemical-transport modeling Satellite remote sensing offers a new and exciting way to make global measurements over extended periods of time, and will hopefully add the larger geographical and seasonal context to point measurements David Edwards, NCAR

3. New MOPITT V3 data 700 hPa 1-12 Nov. 2000 The global impact of biomass burning on the tropical CO distribution is very apparent David Edwards, NCAR

4. Combining sensor data to provide a clearer picture of tropospheric chemistry: Tropospheric Ozone in the South Atlantic MOPITT 700 hPa CO & TRMM Fires • Analysis of the fire count data from TRMM/VIRS shows that the maximum southern burning season occurs in ASO • High EP/TOMS tropical tropospheric ozone values correlate well with the burning plume as indicated by the high CO levels measured by MOPITT Sept. 20-28 2000 EP/TOMS TTO 60 DU Sept. 25 2000 Anne Thompson, NASA David Edwards, NCAR

5. Providing global context to local measurements: Long-range transport of biomass burning products MOPITT CO total column, Oct. 1-15, 2000 October 1-15, 2001 • MOPITT and ground-based FTIR CO total column measurements taken at Lauder, New Zealand. FTIR data provided by N. Pougatchev, NASA, & N. Jones, NIWA • The plume from biomass burning causes a peak in the measured CO in the usually clean air over New Zealand David Edwards, NCAR

6. The Tropical Tropospheric Ozone “Paradox” EP/TOMS tropospheric ozone column from the modified residual method (TRMM/VIRS) fire product Jan. 2001 Jan. 2001 Jan. 5-13 2001 Anne Thompson, NASA Most of the NH biomass burning occurs north of the ITCZ, while the maximum tropical tropospheric O3 columns are noted south of the ITCZ leading to the “ozone reversal” - Thompson et al., GRL 27, 3317 2000 David Edwards, NCAR

7. MOZART-2 Ozone Jan. 2001 700 mb 435 mb Mozart-2 CTM simulation using NCEP winds shows that the Atlantic ozone distribution in the early part of the year has two maxima: • the first is in the lower troposphere over the northern biomass burning region • the second is due to lightning NOX over Africa and South America which forms a mid-troposphere O3 plume extending out over the southern tropical Atlantic David Edwards, NCAR

8. Terra/MOPITT CO 350 hPa Fire Count Jan. 2001 • Very good correlation is seen between the MOPITT CO plume retrievals and the positions of the springtime fires • Clear indication of significant convection and net southern transport from the burning region across the equator and into the Gulf of Guinea 700 hPa ppbv MOPITT monthly mean gridded CO for Jan. 01 David Edwards, NCAR

9. Seven day trajectories calculated using NCEP winds for Jan. 15-22 2001. Positions of trajectory initialization defined by locations of the TRMM fire observations with an initial injection altitude of 3 km CO Cloud Harmattan Monsoon Transport from the Biomass Burning Region ITCZ SH NH David Edwards, NCAR

10. MOPITT Measurements Indicating Convection • Low altitude CO concentrations are high in the NH near the intense burning in East Africa • Emissions are caught in the Harmattan flow, and subsequent convection and interhemispheric transport occurs near the ITCZ • The latitudinal gradient of CO reverses at high altitude, with maximum values observed in the SH ppbv Latitudinal cross-section at 12 E of MOPITT CO with altitude, Jan 20-27 2001 Latitude David Edwards, NCAR

11. MOZAIC and MOPITT MOZAIC flight, 26 Feb., 2001 MOPITT CO at 250 hPa 25-27 Feb., 2001 Douala Brazzaville MOZAIC flight: Brazzaville (4.37 S, 15.46 E) to Douala (4.01 N, 9.72 E). Ozone distribution along flight path correlates well with MOPITT CO . David Edwards, NCAR

12. ERS-2/GOME TroposphericVertical Column NO2 • GOME residual tropospheric NO2 vertical columns also show good correlation with fire locations • Resulting distribution is similar to the CO plumes observed by MOPITT • Industrial hotspots are also evident over Lagos and Johannesburg • High NO2 over southern Africa is most likely a signature of lightning in the area Jan. 2001 mean GOME tropospheric NO2 David Edwards, NCAR

13. The Role of Lightning • Observations of lightning flashes by the TRMM/LIS instrument show significant activity over southern Africa • Upper troposphere lightning NOx is a precursor to O3 • Ozone is formed over Africa and in the plume extending westward into the Atlantic • This is most likely the source of the SH O3 maximum observed in the TOMS tropospheric ozone products LIS Lightning Distribution Jan. 2001 David Edwards, NCAR

14. Conclusions • The new tropospheric satellite sensor data will play an increasingly important role in explaining chemistry and transport processes • This will be complimentary to continued in-situ measurements and modeling studies • The potential for combining measurements from several sensors, such as MOPITT CO, GOME NO2, TRMM fire and lightning counts, provides a powerful tool for investigating the tropospheric production of ozone precursors • MOPITT CO provides a clear picture of the pollution plumes that result from biomass burning and can be used to study convection and advection processes • This suggests that O3 resulting from the north African springtime fires does not reach far enough south to explain the observed TOMS TTO maximum in the southern tropical Atlantic, which is most likely due to lightning NOx produced over southern Africa and South America • Ongoing studies are using data from several satellite sensors to help distinguish biomass burning, lightning, and biogenic sources of O3 precursors to further explain the seasonal variation of the tropical tropospheric O3 distribution David Edwards, NCAR