Recent Trend of Stratospheric Water Vapor and Its Impacts

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Recent Trend of Stratospheric Water Vapor and Its
Impacts

• Steve Rieck, Ning Shen, Gill-Ran Jeong
• EAS 6410
• Team Project
• Apr 20 2006

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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

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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

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Dehydration Mechanism

• 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
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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
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Processes Controlling Interannual SWV

• 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
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Long Term SWV Trend

• Difficulty for long term SWV trend assessment
• Lack of global coherent trend perspectives
• Large measurement uncertainty

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Chemical Sources of Stratospheric H2O

• Chemical source from Methane oxidation
• Methane Oxidation is the primary anthropogenic
  source

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Methane Oxidation

• Methane produces water by the following reaction
• CH4 OH ? CH3 H20
• Accounts for 90 of atmospheric Methane loss

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Simulation of Stratospheric Water Vapor
TrendsImpact 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.

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Approach to SWV Impact on O3 Destruction Chemistry
H2O_Chemistry H2O_Background H2O_Perturbation
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Ozone Destruction Resulting from Perturbation of
SWV

• 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)
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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

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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 O3
  reduction
• Increasing SWV leads to a stronger greenhouse
  effect

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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

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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

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• Questions?