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Atmospheric Aerosols:What they are and why/how I study them             Geeta Persad        PECS Student Presentation
What is an aerosol?• Particles in the atmosphere, both natural and anthropogenic                                          ...
Why might we care about aerosols?Aerosols reduce the amount of solar radiation at the  surface by scattering and absorbing...
How can aerosols affect the climate?• Direct Effects: Scattering/reflection of solar radiation  by particles cools the pla...
How can aerosols affect the climate? • Indirect Effects: Aerosols that can condense water   form the nucleus for cloud dro...
How can aerosols affect the climate?• Semi-Direct Effects: Atmospheric heating from  absorbing aerosols can change cloud f...
How can aerosols affect the climate?• Clouds are a major regulator of Earth’s climate.
How can aerosols affect the climate?                       • Aerosols have                         counteracted CO2       ...
General Circulation Models                     Components:                     -Ocean                     -Land           ...
Radiative Forcing of Black CarbonCharacteristics of an optimal forcing calculation:    – (1) proxy for the change in globa...
Radiative Forcing of Black CarbonCharacteristics of an optimal forcing calculation:    – (1) proxy for the change in globa...
Black Carbon/Climate Interactions           Incoming Solar                                          Semi-direct Effect    ...
Radiative Flux Perturbation• Subsiding regions primarily respond via semi-direct effect,• Convective regions respond prima...
Radiative Flux Perturbation                      Deep Convective RegionsRadiative Flux Perturbation (W/m2)      Change in ...
Radiative Flux Perturbation                               Deep Convective Regions  Change in Temperature (K)         in co...
Solar Dimming and Brightening(Wild, M.; BAMS, 2012 = Great review article)
Solar Dimming and Brightening(Wild, M.; BAMS, 2012 = Great review article)
Solar Dimming and Brightening
Solar Dimming and Brightening  NH SW Surface Rad. - Clear            NH SW Surface Rad. - Cloudy•Understanding why the mod...
Solar Dimming and Brightening•NH Precipitation Anomalies: Driven by aerosols? How and why?
Summary• Aerosols = major issue for climate and the environment• Aerosols counteract CO2 warming    • ?? How much ??    • ...
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Transcript of "Geeta persad aerosol presentation "

  1. 1. Atmospheric Aerosols:What they are and why/how I study them Geeta Persad PECS Student Presentation
  2. 2. What is an aerosol?• Particles in the atmosphere, both natural and anthropogenic Organic Matter Sea Salt Black Carbon Sulfate DUST http://en.wikipedia.org http://www.andaman.org/BOOK/originals/Weber-Toba/pinatubo.jpg
  3. 3. Why might we care about aerosols?Aerosols reduce the amount of solar radiation at the surface by scattering and absorbing sunlight.• Impact on energy sources: solar power yield, agriculture• Air quality impacts on health and quality of life• Product of energy sources: coal, oil and gas, biomass burning• Climate
  4. 4. How can aerosols affect the climate?• Direct Effects: Scattering/reflection of solar radiation by particles cools the planet.
  5. 5. How can aerosols affect the climate? • Indirect Effects: Aerosols that can condense water form the nucleus for cloud droplets. http://earthobservatory.nasa.gov/Library/Aerosols/ http://earthobservatory.nasa.gov/Library/Aerosols/Large Droplets Lower Surface Area Small Droplets Higher Surface Area Lower Reflectivity Higher Reflectivity Shorter Lifetime Longer Lifetime More Precipitation Less Precipitation
  6. 6. How can aerosols affect the climate?• Semi-Direct Effects: Atmospheric heating from absorbing aerosols can change cloud field. Incoming Solar Saturated Vapor Pressure Re-emitted Infrared
  7. 7. How can aerosols affect the climate?• Clouds are a major regulator of Earth’s climate.
  8. 8. How can aerosols affect the climate? • Aerosols have counteracted CO2 warming in the past, but by exactly how much is unclear. • Aerosols are predicted to decrease in the future. • How much additional CO2 warming will this decrease “reveal”?
  9. 9. General Circulation Models Components: -Ocean -Land -Sea Ice -Atmospheres Aerosols Clouds
  10. 10. Radiative Forcing of Black CarbonCharacteristics of an optimal forcing calculation: – (1) proxy for the change in global surface temperature – (2) means for comparing and aggregating results across models or Fi, Fa or Fs(IPCC, 2007: Chapter 2; Hansen et al., 2005)
  11. 11. Radiative Forcing of Black CarbonCharacteristics of an optimal forcing calculation: – (1) proxy for the change in global surface temperature – (2) means for comparing and aggregating results across models or Fi, Fa or Fs Good at (2), Bad at (1) Good at (1), Bad at (2)?
  12. 12. Black Carbon/Climate Interactions Incoming Solar Semi-direct Effect Re-emitted Infrared• Black carbon heating can affect clouds dynamically andthermodynamically•Clouds are a major source of uncertainty in GCMs
  13. 13. Radiative Flux Perturbation• Subsiding regions primarily respond via semi-direct effect,• Convective regions respond primarily via dynamical impacts.• Robust semi-direct effect dominates the RFP signature. (Persad et. al; Journal of Climate, 2012)
  14. 14. Radiative Flux Perturbation Deep Convective RegionsRadiative Flux Perturbation (W/m2) Change in Mid Cloud Amount (%)• For black carbon above the cloud layer, there is an increase in outgoing shortwave radiation.• Increase in radiation is concurrent with an increase in middle cloud amount.
  15. 15. Radiative Flux Perturbation Deep Convective Regions Change in Temperature (K) in convective mass flux* in Cloud Amount (%) • Dominated by dynamical effects of black carbon heating. • Decrease in cloud amount at level of black carbon heating due to inversion and detrainment into large-scale environment. • Above detrainment, latent heat release balances decreased convective heating, maintaining high cloud level. • Mixture of first order physics and parameterization.* Units of (10 3 kg m 2 s 1)
  16. 16. Solar Dimming and Brightening(Wild, M.; BAMS, 2012 = Great review article)
  17. 17. Solar Dimming and Brightening(Wild, M.; BAMS, 2012 = Great review article)
  18. 18. Solar Dimming and Brightening
  19. 19. Solar Dimming and Brightening NH SW Surface Rad. - Clear NH SW Surface Rad. - Cloudy•Understanding why the model does or does not recreate the solardimming and brightening trend may be useful for analyzing theperformance of different mechanisms in the model.
  20. 20. Solar Dimming and Brightening•NH Precipitation Anomalies: Driven by aerosols? How and why?
  21. 21. Summary• Aerosols = major issue for climate and the environment• Aerosols counteract CO2 warming • ?? How much ?? • ?? Why exactly ??• In order to predict future climate change due to CO2, we need tounderstand how past climate has changed due to CO2, which requiresseparating out the effect of aerosols.• My work: • Focused on addressing this issue using general circulation models. • Using observed trends to validate model processes to get a better understanding of how the real world responds to aerosols.
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