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FACTORS GOVERNING THE SEASONAL VARIABILITY OF ATMOSPHERIC CARBONYL SULFIDE

FACTORS GOVERNING THE SEASONAL VARIABILITY OF ATMOSPHERIC CARBONYL SULFIDE. Parv Suntharalingam Harvard/Univ. of East Anglia A.J. Kettle, S. Montzka, D. J. Jacob. GEOS-Chem Meeting April 12 th , 2007.

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FACTORS GOVERNING THE SEASONAL VARIABILITY OF ATMOSPHERIC CARBONYL SULFIDE

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  1. FACTORS GOVERNING THE SEASONAL VARIABILITY OF ATMOSPHERIC CARBONYL SULFIDE Parv Suntharalingam Harvard/Univ. of East Anglia A.J. Kettle, S. Montzka, D. J. Jacob GEOS-Chem Meeting April 12th, 2007

  2. Carbonyl Sulfide (COS) Uptake by Leaf During Photosynthesis Can Carbonyl Sulfide help in Constraining Estimates of Global Primary Production ? COS CO2 COS CO2 GPP : Gross flux of CO2 converted to organic matter during photosynthesis COS and CO2 are taken up through leaf stomata during photosynthesis

  3. SH SEASONAL CYCLES OF COS and CO2COS measurements : S. Montzka (NOAA-GMD) COS CO2 J F M A M J J A S O N D J F M A M J J A S O N D Seasonal cycles of COS and CO2 are correlated, especially at forested sites. CAN COS MEASUREMENTS CONSTRAIN BIOSPHERIC CO2 UPTAKE ? Significant uncertainties remain on aspects of COS budget

  4. SOURCES AND SINKS OF ATMOSPHERIC CARBONYL SULFIDE COS Mean atmospheric conc. ~ 500 ppt

  5. SOURCES AND SINKS OF ATMOSPHERIC CARBONYL SULFIDE COS Oxidation CS2 DMS OCEAN ANTHROPOGENIC

  6. SOURCES AND SINKS OF ATMOSPHERIC CARBONYL SULFIDE Tropospheric Oxidation, Stratospheric Photolysis COS Oxidation CS2 DMS OCEAN PLANTS SOILS ANTHROPOGENIC

  7. SOURCES AND SINKS OF ATMOSPHERIC CARBONYL SULFIDE Tropospheric Oxidation, Stratospheric Photolysis Uncertainty remains on source/sink fluxes COS Oxidation CS2 ?? ?? DMS ?? ?? OCEAN Biomass Burning PLANTS SOILS ANTHROPOGENIC

  8. ATMOSPHERIC COS BUDGETKettle et al. [2002]: Gridded Fields ANNUALLY BALANCED BUDGETTotal sources/sinks :460 Gg S/year -238 -130 -92 280 -180 Not included here Biomass Burning : 35 Tg S (8%) Stratospheric Photolysis : 16 Tg (3.5%) Minor sources : < 3% Also based on : Chin and Davis, 1993; Watts, 2000

  9. OUTLINE • Model atmospheric COS with recent best estimates of seasonal sources and sinks [Kettle et al. 2002] • Evaluate against measurements from global observation network [Montzka et al. 2006] • Which processes govern observed seasonal variability ? Can we improve estimates of prior COS fluxes? AIM :Improved constraints on factors governing COS seasonal variability

  10. COS SURFACE OBSERVATION NETWORK : NOAA-GMD Flask measurements since 2000 [Montzka et al. 2006] Barrow (BRW) • alt • brw • lef mhd • • • hfm nwr • • kum mlo Mauna Loa (MLO) • smo • cgo South Pole (SPO) spo

  11. GEOS-Chem COS SIMULATION • INPUT FLUX DISTRIBUTIONS [Kettle et al. 2002] • SOURCES • Ocean (Direct; CS2 and DMS oxidation to COS) • Anthropogenic (Direct and CS2 oxidation to COS) • SINKS • Terrestrial plant uptake • Soil uptake • COS oxidation by OH (tropospheric) • To be Implemented • Biomass burning • Stratospheric photolysis GEOS-Chem Version 7-03-06 Resolution : 2x2.5; 30 vertical levels Meteorology Year : 2001

  12. COS SINK DISTRIBUTIONS[Kettle et al. 2002] Soil Uptake (JAN) Plant Uptake (JAN) pmol/m2/sec Soil Uptake (JUL) Plant Uptake (JUL) Soil uptake based on soil moisture and temperature. (Only 1 soil type) Plant fluxes derived from NPP and NDVI fields

  13. COS SOURCE DISTRIBUTIONS[Kettle et al. 2002] Anthropogenic (JAN) Ocean (JAN) pmol/m2/sec Anthropogenic (JUL) Ocean (JUL) Ocean fluxes based on ocean photochemical model and DMS distributions Anthropogenic COS fluxes distributed according to SO2 emissions (GEIA 1985)

  14. SEASONAL VARIABLITY OF COS FLUXESFlux Distributions :Kettle et al [2002] Southern Hemisphere Northern Hemisphere OCEAN ANTH. OCEAN Gg S per month SOILS PLANT TOTAL SURFACE COS FLUX • AGGREGATED FLUXES • N Hemisphere variability driven by plant uptakeand ocean fluxes • S Hemisphere variability driven by ocean fluxes

  15. SEASONAL ANOMALIES AT MEASUREMENT SITESData : S. Montzka (NOAA-GMD) Cape Grim, Tasmania South Pole • Seasonal cycle has similar phase at Southern Hemisphere and Northern Hemisphere sites • Northern Hemisphere sites show larger seasonal amplitude Barrow, Alaska Park Falls, Wisconsin Data for years 2001-2005

  16. SEASONAL CYCLE AT REMOTE/OCEAN SITESObservations and Model : Seasonal Anomalies X Observations Model • Good agreement at Southern Hemisphere remote/ocean sites

  17. SEASONAL CYCLE AT REMOTE/OCEAN SITESObservations and Model : Seasonal Anomalies X Observations Model • Good agreement at Southern Hemisphere remote/ocean sites • Observed seasonality not well reproduced as move northwards

  18. SEASONAL CYCLE AT TERRESTRIAL STATIONS Observations and Model : Seasonal Anomalies Observed seasonal cycle not well simulated at Northern Hemisphere terrestrial sites X Observations Model

  19. GLOBAL PLANT UPTAKE OF COS SUMMARY OF ESTIMATES : (Table 4 : Sandoval-Soto et al. 2005)Units : Tg COS/year Kettle et al. [2002] NPP-based estimate is lowerthan recent estimates

  20. SEASONAL CYCLE AT TERRESTRIAL SITES Increased Model Plant COS Uptake (Factor of 3) Increased COS uptake by plants better matches observed seasonality ORIG MODEL X Observations Original Model Model: Increased plant uptake INCREASED UPTAKE MODEL

  21. SEASONAL CYCLE AT TERRESTRIAL SITES Increased Model Plant COS Uptake (Factor of 3) • BUT • Now need an additional source (for balanced annual budget) X Observations Original Model Increased plant uptake

  22. SEASONAL CYCLE AT TERRESTRIAL SITES Increased Model Plant COS Uptake (Factor of 3) • BUT • Now need an additional source (for balanced annual budget) • Phase problems remain X Observations Original Model Increased plant uptake

  23. SEASONAL CYCLE AT TERRESTRIAL SITES Increased Model Plant COS Uptake (Factor of 3) • BUT • Now need an additional source (for balanced budget) • Phase problems remain • Missing source flux ? X Observations Original Model Increased plant uptake

  24. SUMMARY • Primary influences on COS seasonal cycle : Ocean fluxes in Southern Hemisphere; Plant uptake and ocean fluxes in Northern Hemisphere. • Increasing plant uptake of COS by a factor of 3 (to 0.7 Tg S/year) improves model representation of seasonal cycle at terrestrial sites • But, annual COS budget no longer in balance – missing source ? ONGOING/PLANNED WORK • Add source and sink for biomass burning and stratospheric photolysis • Update anthropogenic COS emissions based on latest SO2 inventories. • Inverse model analysis of COS measurements to improve source/sink flux estimates

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