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Organic aerosol and its climate impact

2013 FL A&WMA Conference. Organic aerosol and its climate impact. Min Zhong and Myoseon Jang Sept. 24, 2013 Department of Environmental Engineering Sciences University of Florida. Aerosol: Key to improve climate prediction. cooling. heating. Green House Gases, small uncertainty.

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Organic aerosol and its climate impact

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  1. 2013 FL A&WMA Conference Organic aerosol and its climate impact Min Zhong and Myoseon Jang Sept. 24, 2013 Department of Environmental Engineering Sciences University of Florida

  2. Aerosol: Key to improve climate prediction cooling heating Green House Gases, small uncertainty Atmospheric aerosol, large uncertainty Source: IPCC 2007

  3. How aerosol affects climate

  4. 1 Only absorption causes heating 2 Why study aerosol light absorption? Only a few types of aerosol absorb light, BC, OC, and mineral dusts.

  5. POA & SOA VOC Emissions Oxidation Reactions (OH, O3, NO3) Nucleation or Condensation Secondary Organic Aerosol Primary Organic Aerosol Direct Emission

  6. Role of OC in climate forcing 1. OC is 95 wt% of carbonaceous aerosol 2. Climate effect of OC has been poorly understood global OC budget (154 Tg/yr) Source: IPCC 2007 • Current model assumption: OC has no light absorption • (Maria et al. 2004 ; Hoyle et al. 2009) • Recent research: OC has light absorbing capacity, d-limonene SOA, POA • (Bones et al. 2010; Laskin et al. 2010 ) SOA Black carbon Non-absorbing aerosol POA Motivation: What is the role of OC in climate system?

  7. Objectives To quantify aerosol’s climate impact, light absorption parameter is required. MAC: mass absorption cross section (m2/g) Light absorption property POA SOA Warming or cooling

  8. Light absorption measurement Principle of the method: Beer Lambert’s law ln(I0/I)= bvV/A Integrating sphere ln(I0/I)=CbvV/A How to obtain mass absorption cross section(MAC) ? detector MAC = bv /M UV/Vis light bv: absorption coefficient (m-1) V: the volume of air drawn through the filter during a given sampling time, A is the area of the sample spot, M: aerosol mass concentration, C=1.4845 filter sample

  9. SOA experiments • SOA UV-Vis spectra recording pump filter holder UV lamp 2 m3 Teflon Chamber NOx O3 GC-FID SMPS UV/Vis light RUV-IS filter sample VOCs, NOx Inorganic seed SOA generation

  10. MAC of SOAs α-pinene (AP) Toluene (TOL) d-limonene (DL) • MAC of TOL is 10 times higher than DL and AP • more double bond , higher light absorbing Zhong and Jang, AE, 2011

  11. POA experiment East West 52m3 52m3 T/RH TUVR T/RH TUVR Wood smoke NOx O3 GC-MS OC/EC SMPS TEOM Hickory wood Smoldering burning to reduce the formation of BC RUV-IS FTIR

  12. MAC of POA • Increase in morning: chromophore formation in SOA or POA • Decrease in afternoon: sunlight bleach Zhong and Jang, ACPD, 2013

  13. Radiative forcing of organic aerosol SOA = POA = Sulfate ? • RF of SOA is -0.09 ~ -0.06 w/m2 (Hoyle et al. 2009) “Aerosol optical properties of SOA were taken to be similar to POA” (Hoyle et al. 2009). • In Myhre et al. (2007), they assume POA optical properties are equal to sulfate…

  14. Optical parameters from Mie calculation Extinction cross section Aerosol asymmetry factor Single scattering albedo 1. Particle size distribution assume lognormal distribution, with count median diameter of 138nm, geometric standard of 2 nm (Kaul at el. 2012) 2. Complex refractive index • assume n=1.44 (measured by Kim and Paulson, 2013), • same from 280nm to 900nm. • k is from my measurement Mie code from: http://www.hiwater.org/, shared by Dr. Tami Bond

  15. Optical parameters Aerosol asymmetry factor Single scattering albedo Extinction cross section • Extinction cross section: similar • Asym >0 scattering in the forward direction • SSA (SOA) > SSA(POA) Mie code from: http://www.hiwater.org/

  16. First estimation of radiative impact Chylek, P. and Wong, 1995 • SOA and sulfate are similar, cooling aerosol • POA is warming aerosol. • It should be cautious to replace with each other. SOA = Sulfate ≠POA • simple radiative efficiency: watts/(cm3 aerosol) Radiative efficiency code from: http://www.hiwater.org/

  17. Conclusions • MAC of toluene SOA was the highest compared with MAC values for α-pinene SOA and d-limonene SOA • MAC of POA increased in the morning and decreased in the afternoon due to the competition between chromophore formation and sunlight bleaching • SOA is a cooling aerosol, with negative radiative forcing similar to sulfate. POA is a warming aerosol, with positive net forcing

  18. Acknowledgment This work was supported by grants from the National Science Foundation (ATM-0852747) and the Alumni Scholarship from the University of Florida.

  19. Thank you Questions?

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