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

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

3. 3 Direct effect Indirect effect scattering absorbing modifying cloud properties How aerosol affects climate

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

5. 5 VOC Emissions Oxidation Reactions (OH, O 3, NO 3 ) Nucleation or Condensation S econdary O rganic A erosol Direct Emission P rimary O rganic A erosol POA & SOA

6. Role of OC in climate forcing 6 global OC budget (154 Tg/yr) 1. OC is 95 wt% of carbonaceous aerosol Source: IPCC 2007 2. Climate effect of OC has been poorly understood  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 ) Motivation: What is the role of OC in climate system? Black carbonNon-absorbing aerosol POA SOA

7. Objectives 7 MAC: mass absorption cross section (m 2 /g) Light absorption property Warming or cooling POA SOA To quantify aerosol’s climate impact, light absorption parameter is required.

8. Light absorption measurement 8 Principle of the method: Beer Lambert’s law ln(I 0 /I) = b v V/A filter sample detector UV/Vis light Integrating sphere b v : 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 MAC = b v /M How to obtain mass absorption cross section(MAC) ? ln(I 0 /I) =C b v V/A

9. SOA experiments 9 SOA generation  SOA UV-Vis spectra recording filter sample UV/Vis light RUV-IS 2 m 3 Teflon Chamber NO x O 3 GC-FID SMPS VOCs, NO x Inorganic seed UV lamp pump filter holder

10. MAC of SOAs d-limonene (DL) α-pinene (AP) Toluene (TOL)  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 11 EastWest 52m 3 TUVR T/RH GC-MSOC/EC NO x O3O3 SMPS RUV-IS TEOM FTIR Wood smoke Smoldering burning to reduce the formation of BC Hickory wood

12. MAC of POA 12  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 13  RF of SOA is -0.09 ~ -0.06 w/m 2 (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… SOA = POA = Sulfate ?

14. Optical parameters from Mie calculation 14 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 Bondhttp://www.hiwater.org/ Extinction cross sectionAerosol asymmetry factor Single scattering albedo

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

16. 16 First estimation of radiative impact  simple radiative efficiency: watts/(cm 3 aerosol) Chylek, P. and Wong, 1995 1.SOA and sulfate are similar, cooling aerosol 2.POA is warming aerosol. 3.It should be cautious to replace with each other. Radiative efficiency code from: http://www.hiwater.org/ SOA = Sulfate ≠ POA

17. Conclusions 17 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. 18

19. 19 Thank you