Recent Trend of Stratospheric Recent Trend of Stratospheric Water Vapor and Its ImpactsWater Vapor and Its Impacts

Steve Rieck, Ning Shen, Gill-Ran JeongEAS 6410

Team ProjectApr 20 2006

OverviewOverview

• 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

MotivationMotivation

• 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

Dehydration MechanismDehydration 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

Two-steps process involving these two assumptions

Isotope

(Deuterium)

General Image of SWV TrendGeneral 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

• 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

Processes Controlling Interannual SWVProcesses Controlling Interannual SWV

Quoted: Simulation of Interannual Variance of Stratospheric Water Vapor, Marvin A. Geller, et, al. 2001 Journal of the Atmospheric Science

ENSO Typical Pattern

Long Term SWV TrendLong Term SWV Trend

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

Sample of Decreasing TrendSample of Increasing Trend

Chemical Sources of Stratospheric HChemical Sources of Stratospheric H22OO

• Chemical source from Methane oxidation

• Methane Oxidation is the primary anthropogenic source

Methane OxidationMethane Oxidation

• Methane produces water by the following reaction:

CH4 + OH CH3 + H20

• Accounts for 90% of atmospheric Methane loss

• 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.

• 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

Simulation of Stratospheric Water Vapor Trends:Simulation of Stratospheric Water Vapor Trends:Impact on Stratospheric Ozone ChemistryImpact on Stratospheric Ozone Chemistry

H2O_Chemistry = H2O_Background + H2O_Perturbation

Table 1. Overview of analyzed model experimentsEXP H2O perturbation simulation periodCNTL 0 ppmv, reference simulation 11 yearsVOLC 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 yearsH2O_5 5 ppmv, long-term increase 11 years

Approach to SWV Impact on OApproach to SWV Impact on O33

Destruction ChemistryDestruction Chemistry

Zonally averaged volume mixing ratio of the water vapor perturbation (ppmv).

• 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

JAN

JULY

Zonally and Monthly averaged changes of OH (Left) and Ozone (Right)

• Heterogeneous reactions on PSCs and sulfate aerosols in CHEM:

HCl + ClONO2 Cl2 + HNO3

H2O + ClONO2 HOCl + HNO3

HOCl + HCl Cl2 + H2O

N2O5 + H2O 2HNO3

80N 50mb 80S 50mb

Ozone Destruction Resulting from Ozone Destruction Resulting from Perturbation of SWVPerturbation of SWV

50% increase (20 ~ 25 x 105 molec/cm3)

10%

7%

Water Vapor and the Greenhouse EffectWater Vapor and the Greenhouse Effect

• By far the most effective greenhouse gas

More H2O

Higher Temperature

More Evaporation

• Responsible for 50-60% of natural global warming Effect

• Lead to a positive feedback loop

• 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

SummarySummary

Take Home MessagesTake 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

More ReferenceMore 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

Questions?