Stratospheric Ozone : Depletion and Recovery

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Stratospheric Ozone Depletion and Recovery
Eun-Su Yang1, Ross J. Salawitch2, Derek Cunnold3,
Michael J. Newchurch1, M. Patrick McCormick4,
James Russell III4, Joseph Zawodny5, Sam
Oltmans6 1 Univ of Ala, Huntsville, 2 Univ of
Md, 3 Ga. Tech, 4 Hampton University, 5 NASA
LaRC, 6 NOAA ESRL
Motivation
Ground Based
TOMS
OMI
How much of this leveling off in ozone column
is due to the leveling off of halogens ?
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WMO 2007 (Chapter 6) First Stage of Ozone Recovery
The occurrence of a statistically
significant reduction in the rate of decline of
ozone due to changing ozone depleting substances
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First Stage of Ozone Recovery Slowing of
Decline 1997 is the Critical Time to look for
recovery of Polar Ozone
EESC Equivalent Effective Stratospheric
Chlorine
1997
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Complication 1
Large year to year variability in temperature
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Complication 2
Ozone reaches zero over considerable height
range. This saturation effect may be the cause
of the leveling off of the column ozone time
series
NOAA ESRL Ozonesonde Data http//www.esrl.noaa.g
ov/gmd/dv/spo_oz/sondes
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Extra-Vortex
Collar
Vortex
Equivalent Latitude
Equivalent Latitude
Data sources ? SAGE II, HALOE, Sondes,
Brewer/Dobson ? Classify data as vortex,
collar, or extra vortex using Equivalent
latitude at 440 K (Nash criteria PV from NCEP
reanalysis)
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Total Ozone October, Vortex Core
Record Cold
Ozone (DU)
Early Warming
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Scatter plot, Detrended Total O3 vs Detrended
Temperature (440 K)
Cold winters associated with larger vortices and
less ozone, due to combination of dynamical
effects and chemical effects related to
availability of PSCs (Boedeker et al., 2002
Newman et al., 2004 Huck et al., 2005)
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Scatter plot, Detrended Total O3 vs Detrended
Temperature (440 K)
We use slopes of these curves, together with
yearly T residual, to derive Ozone Time Series
that account for yearly variations in
temperature and dynamics
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Total Ozone October, Vortex Core
Record Cold
Ozone (DU)
Early Warming
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Total Ozone October, Vortex Core
? Have dealt with Complication 1
(Meteorology) ? Now, must deal with Complication
2 (Loss Saturation)
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Loss Saturation, Method 1 PDFs of Total Column
Ozone
October vortex core mean ozone is 13 DU higher
during 1994 to 2007 time period than predicted
ozone found using O3 vs T residual
relation from 1979 to 1991 time
period September no discernable saturation
effect, in either core or collar October vortex
collar 13 DU effect
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Ozonesondes
SAGE II
Loss Saturation, Method 2 ?(O3) vs
?(T) in layers
October vortex core ozonesonde saturation
effect 10.1 DU (3.1 4.3 2.7)
SAGE II saturation effect
13.6 DU (5.3 4.4 3.9 )
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Ozonesondes
SAGE II
Loss Saturation, Method 2 ?(O3) vs
?(T) in layers
October vortex core ozonesonde saturation
effect 10.1 DU (3.1 4.3 2.7)
SAGE II saturation effect
13.6 DU (5.3 4.4 3.9 )
Adjust Total Ozone Time series by 13 DU (mean
value of loss saturation for 1994 to 2006), with
coldest years having larger adjustments
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Total Ozone October, Vortex Core
Record Cold
Early Warming
Polar EESC
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Trend Analysis
Sept Core
Oct Core
Sept Collar
Oct Collar
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Black Cumulative Sum of Residuals (i.e.,
deviation of data from fit)
CUSUM Analysis
Sept Core
Oct Core
Sept Collar
Blue dotted 95 confidence limit
Oct Collar
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Conclude ? Antarctic Ozone, within both core
and collar regions, is in first stage of
recovery due to the leveling off of ozone
depleting substances ? In plain English
chemical loss is not getting any worse
(use of word recovery seems strange to me,
but the community has chosen this
word to describe this situation!) ? Yearly
variations in Antarctic ozone are now driven by
meteorology ? Cold winters ? low ozone ?
Next stage of recovery (actual improvement in
ozone) not likely to occur until middle of
next decade (Newman et al., GRL, 2006)