the impact of volcanic aerosols on stratospheric chemistry with implications for geoengineering...
TRANSCRIPT
The impact of volcanic aerosols on stratospheric chemistry with
implications for geoengineeringSimone Tilmes ([email protected])
WACCM team, Doug Kinnison, Rolando Garcia, Anne Smith, Ryan Neely, Andrew Conley, Jean-Francois Lamarque
Rolf Müller, Ross Salawitch, Tim Canty, Julia Jee-Taylor, Sasha Madronich, Kelly Chance
SSiRC: 28 - 30 October 2013, Atlanta, Georgia, USA
The impact of volcanic aerosols on stratospheric chemistry with
implications for geoengineering
• Impact of volcanic aerosols on total ozone• Changes in chemical reaction rates with enhanced aerosols• Importance of the aerosol distribution of polar ozone loss• Importance of very short-lived species on the example of
geoengineering
• Volcanic aerosols have an important impact on ozone, result in a reduction of column ozone of about 3% for El Chichón and 5% for Mt Pinatubo
• Influence up to 5 years
Column Ozone Change
Ground based Observations, WMO 2006
ElChichón
MtPinatubo
Observations, WMO 2010
Total ozone deviations from 1964-80 mean
WACCM (SD)WACCM (no volcanoes, 2000-01 condition)
ElChichón MtPinatubo
NCAR WACCM CCMI Simulations
• WACCM results in slightly lower reduction (1-3%). Changes of chemistry do not explain reduced values of ozone 4 years after the eruption
ElChichón
MtPinatubo
Column Ozone Change
Observations, WMO 2010
Total ozone deviations from 1964-80 mean
Increase of heterogeneous reactions-> decrease of the NOx/NOy equilibrium (Fahey et al., 1993)
(1) N2O5 + H2O -> 2HNO3
(2)ClONO2 + H2O -> HOCl + HNO3 T < 200 K as important as (1)
(3)ClONO2 + HCl -> HNO3 + Cl2
(4)HOCl + HCl -> Cl2 + H2O
-> increase in the ClOx, BrOx and HOx
Impact on Ozone Destroying CyclesSurface Area Density (1992) WACCM Ozone Change (1992)
Difference Volcanic – Clean NOxClOx/BrOx HOxOx,Total Loss
ppmμm2/cm3
New SAD Dataset for CCMI
Impact on Ozone Destroying CyclesSurface Area Density (1992) WACCM Ozone Change (1992) ppmμm2/cm3
New SAD Dataset for CCMI Total Column change
• Ozone depletion depends on temperatures in the polar vortex
• 1992, 1993: Low PSC Formation Potential, however larger Ozone Loss
Arctic Polar Ozone Loss
• Ozone depletion dependent on surface area density (Drdla and Müller, 2012)
• 1992, 1993: line up in relation to ozone
Are models able to simulate high ozone loss in 1993?
Estimation from Observations (HALOE satellite)
Tilmes et al., 2008
Arctic Polar Ozone LossEstimation from Observations WACCM Volcanic – Clean, March 1993
expected impact of volcanic aerosols ~70 DU
~Impact of aerosols (~70DU)
~Impact of aerosols (~70DU)
Arctic Polar Ozone LossEstimation from Observations WACCM Volcanic – Clean, March 1993
SAD μm2/cm3
expected impact of volcanic aerosols ~70 DU (~30%)
simulated reduction around 40 DU Issue: prescribed surface area density field (monthly and zonal averages) are not in alignment with vortex dynamics
Maximum around 40 DU
~Impact of aerosols (70DU)
Arctic Polar Ozone LossEstimation from Observations WACCM Volcanic – Clean, March 1993
expected impact of volcanic aerosols ~70 DU (~30%)
simulated reduction around 40 DU Issue: prescribed surface area density field (monthly and zonal averages) are not in alignment with vortex dynamics
Modified SAD: Ozone loss up to 65 DU
MERRA temperatures too warm?
Maximum around 40 DU Maximum around 65 DU
SAD μm2/cm3
SAD from 1992 + increased high latitudes
% D
iffer
ence
Equivalent Latitude
Impact of Geo-engineering SAD on Ozone in 2040Impact of different assumptions of VSL halogens in the stratosphere
Feb/March/April
% Change in Column Ozone μm2/cm3
Rasch et al., 2008: 2Tg S yr-1, Tropical Injection 10oN-10oS
Surface Area Density (2040)
Aug/Sep/Oct
Equivalent Latitude
Tilmes et al., 2012Considering the impact of VSLS on ozone loss:-Tropics: sign change with very short-lived species-Mid-latitudes: doubling of ozone loss; enhancement of the BrO and HOx catalytic cycles-Polar LMS: significant increase of ozone loss; enhancement of BrOx and ClOx cycles
% D
iffer
ence
Equivalent Latitude
Impact of Geo-engineering SAD on Ozone in 2040Impact of different assumptions of VSL halogens in the stratosphere
Feb/March/April
% Change in Column Ozone μm2/cm3
Rasch et al., 2008: 2Tg S yr-1, Tropical Injection 10oN-10oS
Surface Area Density (2040)
Aug/Sep/Oct
Equivalent Latitude
Tilmes et al., 2012Considering the impact of VSLS on ozone loss:-Tropics: sign change with very short-lived species-Mid-latitudes: doubling of ozone loss; enhancement of the BrO and HOx catalytic cycles-Polar LMS: significant increase of ozone loss; enhancement of BrOx and ClOx cycles
• Volcanic aerosols impact global ozone for up to 5 years • Largest local reduction in the Arctic polar• Aerosol loading critical for models to estimate the
impact of aerosols on ozone• Understanding of the amount of Chlorine and Bromine
critical for impact of potential geoengineering applications on ozone
Summary