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Dalhousie University Department of Physics and Atmospheric Science

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

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Dalhousie University Department of Physics and Atmospheric Science

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  1. Dalhousie UniversityDepartment of Physics and Atmospheric Science Research in Theoretical, Experimental, and Applied Physics • Materials Science • Biophysics • Condensed Matter Physics • Atmospheric Science 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 Kelly Chance Chris Sioris Arlene Fiore

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

  4. ORIGIN OF ATMOSPHERIC AEROSOLS Aerosol: dispersed condensed matter suspended in a gas Size range: 0.001 mm (molecular cluster) to 100 mm (small raindrop) Soil dust Sea salt 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= 2pr/l

  7. Mie Theory Extinction = Scattering + Absorption Extinction Efficiency (Qext) = ratio of the extinction cross section to the geometric cross-section (πr2)

  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=Ioe-

  9. What do we actually see?

  10. Aerosols Visible over Dark Surface Mar 3, 2003

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

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

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

  14. Simplified Tropospheric Ozone (O3) Chemistry hv OH HNO3 NO2 NOx NO O3 OH HOx HO2 H2O2 hv, H2O CO, VOCs CO, VOCs, NOx VOCs + OH  HCHO HCHO + h 2HO2 + CO HCHO + OH  HO2 + CO + H2O Role of Formaldehyde (HCHO)

  15. THE NITROGEN CYCLE: MAJOR PROCESSES combustion lightning ATMOSPHERE N2 NO oxidation HNO3 denitri- fication biofixation deposition orgN decay NH3/NH4+ NO3- BIOSPHERE assimilation nitrification weathering burial LITHOSPHERE

  16. NOx EMISSIONS (Tg N yr-1) TO TROPOSPHERE STRATOSPHERE 0.2 LIGHTNING 6 SOILS 5 FOSSIL FUEL 20 BIOMASS BURNING 5 BIOFUEL 2 AIRCRAFT 0.5

  17. 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 • ~ 106 gridboxes • In global models, this implies a horizontal resolution of 100-500 km in horizontal and ~ 1 km in vertical

  18. 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

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

  20. Retrieval of Trace Gas Column Nonlinear least-squares fitting Solar Io Backscattered intensity IB Scattering by Earth surface and by atmosphere A EARTH SURFACE

  21. Total NO2 Slant Columns Observed from the SCIAMACHY Satellite Instrument May-August 2004

  22. Perform a Radiative Transfer Calculation to Account for Viewing Geometry and ScatteringCloud Screening: Remove Scenes with IB,c > IB,o IB,c IB,o Io q • LIDORT Radiative Transfer Model [Spurr et al., 2002] • FRESCO Clouds Fields [Koelemeijer et al., 2002] • GOME Surface Reflectivity [Koelemeijer et al., 2003] Rc Ro Pc dt Rs

  23. Tropospheric NO2 Columns Observed from the SCIAMACHY Satellite Instrument May-August 2004 detection limit

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

  25. Ozone Control Strategies Require Independent Information on Effectiveness of Reducing NOx or VOCs Shown that the HCHO/NO2 Ratio Is as Indicator That Can be Observed from Space (ppbv) NOx-Saturated NOx-Limited Sillman and He, 2002

  26. GOME Observations Show NOx-Sensitive Conditions Over Most Polluted Regions During AugustMajor Industrial Areas are Clear Exceptions White areas indicate clouds or data below the GOME detection limit August

  27. Biomass Burning Emissions are Clearly NOx-Sensitive, In Contrast with NOx-Saturated Conditions Over the Industrial Highveld Also observe plume evolution August NOx Lim NOx Lim

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

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