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Recent Trend of Stratospheric Water Vapor and Its Impacts

Recent Trend of Stratospheric Water Vapor and Its Impacts. Steve Rieck, Ning Shen, Gill-Ran Jeong EAS 6410 Team Project Apr 20 2006. Overview. Motivation How we look at Stratospheric Water Vapor Physical Aspect Chemical Aspect Impact of Stratospheric Water Vapor Trend

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Recent Trend of Stratospheric Water Vapor and Its Impacts

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  1. Recent Trend of Stratospheric Water Vapor and Its Impacts Steve Rieck, Ning Shen, Gill-Ran Jeong EAS 6410 Team Project Apr 20 2006

  2. Overview • Motivation • How we look at Stratospheric Water Vapor • Physical Aspect • Chemical Aspect • Impact of Stratospheric Water Vapor Trend • Implication from the precursors • Take-Home Message

  3. Motivation • Better understand the process of the entry of water vapor into Stratosphere • Obtain a picture of the Stratospheric Water Vapor (SWV) trend • Study the interactions between the increasing SWV and other atmospheric chemical species • Investigate the impact of SWV over the atmospheric activities

  4. Dehydration Mechanism Isotope (Deuterium) Two-steps process involving these two assumptions • SWV Sources • Surface Evaporation – Dominant • Chemical Reaction – Secondary • Convective Process • Gradual Ascend Process Quoted: How Water Enters the Stratosphere. Karen H. Rosenlof , Science Vol 302 5 DEC 2003

  5. General Image of SWV Trend Quoted: Changes in the distribution of stratospheric water vapor observed by an airborne microwave radiometer Feist, Dietrich G., et al.; 2003

  6. Processes Controlling Interannual SWV ENSO Typical Pattern • Interannual variability of entry value of H2O mixing ratio • Volcanic Eruptions • Brewer-Dobson Circulation • Interannual variability of stratospheric dynamics • Quasi - Biennial Oscillation • El Niño - Southern Oscillation Quoted: Simulation of Interannual Variance of Stratospheric Water Vapor, Marvin A. Geller, et, al. 2001 Journal of the Atmospheric Science

  7. Long Term SWV Trend Sample of Increasing Trend Sample of Decreasing Trend • Difficulty for long term SWV trend assessment • Lack of global coherent trend perspectives • Large measurement uncertainty

  8. Chemical Sources of Stratospheric H2O • Chemical source from Methane oxidation • Methane Oxidation is the primary anthropogenic source

  9. Methane Oxidation • Methane produces water by the following reaction: CH4 + OH  CH3 + H20 • Accounts for 90% of atmospheric Methane loss

  10. Simulation of Stratospheric Water Vapor Trends:Impact on Stratospheric Ozone Chemistry • Motivation • Water vapor in the upper troposphere and lower stratosphere plays a key role in atmospheric chemistry • Oxidation of H2O and CH4: O(1D) + H2O  2OH O(1D) + CH4 OH + CH3 • Objective • To assess the contribution of the simulated water vapor increase the analyzed ozone decrease in the transient model simulation (Dameris et alo., 2005) • To investigate whether these shorter-term ozone change arise from a short-term water vapor increase such as volcanic eruption.

  11. Zonally averaged volume mixing ratio of the water vapor perturbation (ppmv). Table 1. Overview of analyzed model experiments EXP H2O perturbation simulation period CNTL 0 ppmv, reference simulation 11 years VOLC 2 ppmv, July and August, 5 annual cycles July-June short-term increase (last 5 years of CNTL) H2O_1 1 ppmv, long-term increase 11 years H2O_5 5 ppmv, long-term increase 11 years Approach to SWV Impact on O3 Destruction Chemistry H2O_Chemistry = H2O_Background + H2O_Perturbation

  12. Ozone Destruction Resulting from Perturbation of SWV • Heterogeneous reactions on PSCs and sulfate aerosols in CHEM: HCl + ClONO2 Cl2 + HNO3 H2O + ClONO2 HOCl + HNO3 HOCl + HCl  Cl2 + H2O N2O5 + H2O  2HNO3 10% JAN 7% JULY Zonally and Monthly averaged changes of OH (Left) and Ozone (Right) 80N 50mb 80S 50mb • Catalytic ozone destruction cycle: X + O3 XO + O2 XO + O  X + O2 Net: O3 + O  2O2 • Additional HOx-cycle: OH + O3 HO2 + O2 HO2 + O3 OH + O2 + O2 Net: 2O3 3O2 • Coupling of HOx and NOx cycle: OH + NO2 + M  HNO3 + M • Coupling of HOx and ClOx cycle: OH + HCl  H2O + Cl HO2 + ClO  HOCl + O2 • Ozone production in methane oxidation chain: CH3O2 + NO  CH3O + NO2 HO2 + NO  OH + NO2 NO2 + hv  NO + O Net: O2 + O  O3 50% increase (20 ~ 25 x 105 molec/cm3)

  13. Water Vapor and the Greenhouse Effect • By far the most effective greenhouse gas • Responsible for 50-60% of natural global warming Effect • Lead to a positive feedback loop

  14. Summary • The trend of SWV is not globally coherent • Large scale atmospheric circulations and natural events impact the behavior of SWV • The Increasing of SWV leads to enhancing O3reduction • Increasing SWV leads to a stronger greenhouse effect

  15. Take Home Messages • Increasing trend of SWV in some regions • Increasing CH4 leads to increasing SWV • More water vapor leads to more O3 destruction • Positive greenhouse effect of SWV • The increasing trend of SWV needs more investigation • Physical perspective • Chemical perspective • Ecological perspective

  16. More Reference • NOAA Global Monitoring Division • http://www.cmdl.noaa.gov/hotitems/watervapor.html • World Climate Research Program -- Stratospheric Processes And their Role in Climate • http://www.aero.jussieu.fr/~sparc/index.html • Stenke, A., V. Grewe. “Simulation of stratospheric water vapor trends: impact on stratospheric ozone chemistry.” Atmos. Chem. Phys., 5, 1257-1272, 2005

  17. Questions?

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