1. The Impact of Secondary Organic Aerosol Derivatives of Isoprene on Cloud Formation and Albedo Akua Asa-Awuku EAS6410 Term Paper Presentation

2. Summary MotivationMotivation –Biogenic Emissions –Sources of Isoprene Sources of SOA from IsopreneSources of SOA from Isoprene The impact of SOA’s on Cloud FormationThe impact of SOA’s on Cloud Formation Cloud Formation and AlbedoCloud Formation and Albedo Hydrological ImplicationsHydrological Implications

3. The Importance of Biogenic Emissions Amazon has low levels of anthropogenic emissionsAmazon has low levels of anthropogenic emissions Isoprene emissions in US larger than anthropogenic particulate matterIsoprene emissions in US larger than anthropogenic particulate matter Eight Different Vegetation Types are major sources of IsopreneEight Different Vegetation Types are major sources of Isoprene

4. Major Sources of NMHC SourceIsopreneMonoterpeneORVOCOVOC Total VOC Woods37295177177821 Crops2464545120 Shrub103253333194 Ocean002.52.55 Other41229 All5031272602601150 Tg C yr -1

5. What is Isoprene OlefinicOlefinic Highly reactive Double BondsHighly reactive Double Bonds Volatile Organic Compound (VOC)Volatile Organic Compound (VOC) Non-Methane Hydrogen Carbon (NHMC)Non-Methane Hydrogen Carbon (NHMC)

6. Products of Isoprene Photooxidation

7. Derivatives of Photoxidation Assumed to be extremely volatile (e.g formaldehyde)Assumed to be extremely volatile (e.g formaldehyde) Assumed Most likely not to be SOA’sAssumed Most likely not to be SOA’s Two newly identified species hypothesized to be SOA’s from photooxidation of isopreneTwo newly identified species hypothesized to be SOA’s from photooxidation of isoprene Formation of SOA via acidic catalystsFormation of SOA via acidic catalysts

8. Data Collection Data Samples collected from LBA-CLAIRE campaign July 25 -27 [Claeys, 2004]Data Samples collected from LBA-CLAIRE campaign July 25 -27 [Claeys, 2004] AssumptionsAssumptions –Very low Anthropogenic emissions –Tropics site of high photoxidation Samples Subjected to GS-MSSamples Subjected to GS-MS

9. SOA from Isoprene Gas Chromatography results that show presence of a product of isoprene photo- oxidationGas Chromatography results that show presence of a product of isoprene photo- oxidation Similar 5 carbon skeleton as that of isopreneSimilar 5 carbon skeleton as that of isoprene

10. SOA from Isoprene Proposed formation of the 2-methyltetrols from isoprene by reaction with OH’O 2 followed by self-and cross- reactions with radicalsProposed formation of the 2-methyltetrols from isoprene by reaction with OH’O 2 followed by self-and cross- reactions with radicals Intermediate 1,2, diols have been previously reported under low NO x conditions [Ruppert, 2000]Intermediate 1,2, diols have been previously reported under low NO x conditions [Ruppert, 2000]

11. Significance of (1) and (2) SOA’s have low yield from Isoprene photooxidationSOA’s have low yield from Isoprene photooxidation However, large emissions of Isoprene, suggest significant annual formation of SOA’sHowever, large emissions of Isoprene, suggest significant annual formation of SOA’s Estimated 2 Tg per year of (1) and (2) in Amazon BasinEstimated 2 Tg per year of (1) and (2) in Amazon Basin IPCC estimates 8 to 40 Tg of biogenic SOA annuallyIPCC estimates 8 to 40 Tg of biogenic SOA annually Low Vapor Pressure and High HygroscopicityLow Vapor Pressure and High Hygroscopicity

12. SOA’s via Sulfuric Acid Catalysts Urban and Rural Areas contain sufficient amounts of background acidic catalystsUrban and Rural Areas contain sufficient amounts of background acidic catalysts Also significant emissions of Isoprene in these regionsAlso significant emissions of Isoprene in these regions Limbeck explained that proposed pathway contribute to the explanation of HULIS substances on continental EuropeLimbeck explained that proposed pathway contribute to the explanation of HULIS substances on continental Europe

13. Reaction Yield increases with catalystReaction Yield increases with catalyst Influence of ozone as competing oxidantInfluence of ozone as competing oxidant Effect of Relative air HumidityEffect of Relative air Humidity

14. Short Recap SOA’s from Isoprene ExistSOA’s from Isoprene Exist –Photooxidative products have low vapor pressures –Humic-like substances generated from acidic catalysts All SOA’s from Isoprene can be considered to be highly hydroscopicAll SOA’s from Isoprene can be considered to be highly hydroscopic

15. Cloud Formation Kohler EquationKohler Equation –Kelvin Effects Strong functions of Surface TensionStrong functions of Surface Tension Humic-like aerosols decrease σHumic-like aerosols decrease σ

16. Decreasing Surface Tension

17. Kohler Curves

18. Consequences of Surfactants Great Cloud Droplet NumberGreat Cloud Droplet Number –30% decrease in σ yields a 20% increase in droplet number Smaller cloud droplet RadiiSmaller cloud droplet Radii –Average 6% decrease in droplet size Significant Change in Cloud Properties (hence Albedo)Significant Change in Cloud Properties (hence Albedo)

19. Droplet Number and Albedo

20. Albedo and Cloud Optical Thickness

21. Susceptiblity defined as the sensitivity of cloud albedo in comparison to cloud droplet number concentrationdefined as the sensitivity of cloud albedo in comparison to cloud droplet number concentration ten percent increase in droplet number concentration, leads to an increase of 0.75% in albedoten percent increase in droplet number concentration, leads to an increase of 0.75% in albedo

22. Albedo and Cloud Optical Thickness

23. Isoprene Emissions SOA Formation Cloud Formation Cloud Albedo Precipitation/ Water Stress Surface Temperature Hydrological Cycle

24. Conclusions SOA’s from Isoprene do existSOA’s from Isoprene do exist Humic-like SOA’s decrease surface tensions of pure water by 30% increase the droplet number concentration by 20%Humic-like SOA’s decrease surface tensions of pure water by 30% increase the droplet number concentration by 20% 20% increase in droplet number, correlates to a change in top of atmospheric cloud albedo of nearly 1%20% increase in droplet number, correlates to a change in top of atmospheric cloud albedo of nearly 1% a global mean forcing of almost -1 Wm -2 due to SOA’s from Isoprenea global mean forcing of almost -1 Wm -2 due to SOA’s from Isoprene

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