1. Dalhousie University Department of Physics and Atmospheric Science Materials Science Biophysics Condensed Matter Physics Atmospheric Science Research in Theoretical, Experimental, and Applied Physics http://www.physics.dal.ca/files/Physics_and_Atmospheric_Science_Faculty.ppt

2. Ozone and Aerosols in the Lower Atmosphere Randall Martin Aaron Van Donkelaar Arlene Fiore Kelly Chance Chris Sioris

3. GLOBAL RADIATIVE FORCING OF CLIMATE, 1750-present IPCC [2001]

4. ORIGIN OF ATMOSPHERIC AEROSOLS Soil dust Sea salt Aerosol: dispersed condensed matter suspended in a gas Size range: 0.001  m (molecular cluster) to 100  m (small raindrop) Environmental importance: health (respiration), visibility, radiative balance, cloud formation, heterogeneous reactions, delivery of nutrients…

5. COMPOSITION OF PM2.5 (NARSTO PM ASSESSMENT)

6. Scattering of Radiation Size Parameter: xr

7. Mie Theory Extinction = Scattering + Absorption Extinction Efficiency (Q ext ) = ratio of the extinction cross section to the geometric cross-section (πr 2 )

8. MODerate-resolution Imaging Spectroradiometer (MODIS) Seven MODIS bands are available for aerosol properties 0.47, 0.55, 0.65, 0.86, 1.24, 1.64, and 2.13 µm OCEAN reflectance contrast between cloud-free atmosphere and dark ocean aerosol optical thickness for all 7 bands LAND reflectance of dark vegetation and semi-arid regions deduced using 2.13 µm where aerosols are nearly transparent reflectance contrast between atmosphere and dense dark vegetation surface aerosol optical thickness (0.47 and 0.66 µm) Optical Thickness I=I o e - 

9. What do we actually see?

10. Mar 3, 2003 Aerosols Visible over Dark Surface

11. Example Cloud and Aerosol Optical Thickness Aerosol Optical Thickness (550 nm) Cloud Optical Thickness

13. TROPOSPHERIC OZONE IS A KEY SPECIES IN CLIMATE AND AIR QUALITY Tropopause Stratopause Major greenhouse gas Primary constituent of smog Largely controls atmospheric oxidation Stratosphere Troposphere Ozone layer Mesosphere

14. THE ATMOSPHERE IS AN OXIDIZING MEDIUM EARTH SURFACE Emission Reduced gas Oxidized gas/ aerosol Oxidation Uptake Reduction

15. CO, VOCs, NO x HO 2 OH NONO 2 H2O2H2O2 O3O3 hv, H 2 O hv HNO 3 OH VOCs + OH  HCHO HCHO + h   2HO 2 + CO HCHO + OH  HO 2 + CO + H 2 O CO, VOCs Simplified Tropospheric Ozone (O 3 ) Chemistry Role of Formaldehyde (HCHO) NO x HO x

16. THE NITROGEN CYCLE: MAJOR PROCESSES ATMOSPHERE N2N2 NO HNO 3 NH 3 /NH 4 + NO 3 - orgN BIOSPHERE LITHOSPHERE combustion lightning oxidation deposition assimilation decay nitrification denitri- fication biofixation burial weathering

17. NO x EMISSIONS (Tg N yr -1 ) TO TROPOSPHERE FOSSIL FUEL 20 AIRCRAFT 0.5 BIOFUEL 2 BIOMASS BURNING 5 SOILS 5 LIGHTNING 6 STRATOSPHERE 0.2

18. EULERIAN RESEARCH MODELS SOLVE MASS BALANCE (alias CONTINUITY) EQUATION IN 3-D ASSEMBLAGE OF GRIDBOXES Solve continuity equation for individual gridboxes Models can presently afford ~ 10 6 gridboxes In global models, this implies a horizontal resolution of 100-500 km in horizontal and ~ 1 km in vertical

20. BOTTOM-UP EMISSION INVENTORIES ARE NOTORIOUSLY DIFFICULT TO DETERMINE Fuel use estimates Measurements of emission ratios Process studies Estimate biological density Temperature, water, … dependence of biological activity Extreme events

21. Absorbing properties of molecules Atmospheric trace gas absorptions detected in satellite spectra:

22. Retrieval of Trace Gas Column EARTH SURFACE Scattering by Earth surface and by atmosphere Backscattered intensity I B Solar I o A Nonlinear least-squares fitting

23. Total NO 2 Slant Columns Observed from the SCIAMACHY Satellite Instrument May-August 2004

24. Perform a Radiative Transfer Calculation to Account for Viewing Geometry and Scattering Cloud Screening: Remove Scenes with I B,c > I B,o  RcRc RoRo I B,o I B,c PcPc RsRs LIDORT Radiative Transfer Model [Spurr et al., 2002] FRESCO Clouds Fields [Koelemeijer et al., 2002] GOME Surface Reflectivity [Koelemeijer et al., 2003] dd IoIo

25. Tropospheric NO 2 Columns Observed from the SCIAMACHY Satellite Instrument May-August 2004 detection limit

26. Major Urban Centers Are Concentrated NOx Sources May-August 2004 detection limit

27. Sillman and He, 2002 (ppbv) NO x -Saturated NO x -Limited Shown that the HCHO/NO 2 Ratio Is as Indicator That Can be Observed from Space Ozone Control Strategies Require Independent Information on Effectiveness of Reducing NOx or VOCs

28. GOME Observations Show NO x -Sensitive Conditions Over Most Polluted Regions During August Major Industrial Areas are Clear Exceptions August White areas indicate clouds or data below the GOME detection limit

29. Biomass Burning Emissions are Clearly NO x -Sensitive, In Contrast with NO x -Saturated Conditions Over the Industrial Highveld August Also observe plume evolution NO x Lim

30. Seasonal Evolution from NOx-Sensitive to NOx-Saturated Conditions in Fall