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Stratospheric Ozone : Depletion and Recovery. Eun-Su Yang 1 , Ross J. Salawitch 2 , Derek Cunnold 3 , Michael J. Newchurch 1 , M. Patrick McCormick 4 , James Russell III 4 , Joseph Zawodny 5 , Sam Oltmans 6 1 Univ of Ala, Huntsville, 2 Univ of Md, 3 Ga. Tech, - PowerPoint PPT Presentation
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Stratospheric Ozone : Depletion and RecoveryEun-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
How much of this “leveling off”in ozone column is due to the
“leveling off” of halogens ?
TOMSOMI
Ground Based
Motivation:
WMO 2007 (Chapter 6)First Stage of Ozone Recovery
The occurrence of a statistically significantreduction in the rate of decline of ozone
due to changing ozone depleting substances
First Stage of Ozone Recovery – Slowing of Decline1997 is the Critical Time to look for recovery of Polar Ozone
EESC: Equivalent Effective Stratospheric Chlorine
1997
Complication #1
Large year to year variabilityin temperature
Figure courtesy Paul Newman5 K below average
Sep 21-30, 465 K, 65-75 S̊
Apparent downward trend is not significant
First recorded major stratospheric warming leads to split ozone hole in
2002
Figure courtesy Paul Newman5 K below average
Sep 21-30, 465 K, 65-75 S̊
Apparent downward trend is not significant
First recorded major stratospheric warming leads to split ozone hole in
2002
5 K below average
Sep 21-30, 465 K, 65-75 S̊
Apparent downward trend is not significant
First recorded major stratospheric warming leads to split ozone hole in
2002
Complication #2
Ozone reaches “zero” overconsiderable height range.
This “saturation effect” may bethe cause of the “leveling off”
of the column ozone time series
NOAA ESRL Ozonesonde Data: http://www.esrl.noaa.gov/gmd/dv/spo_oz/sondes
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)
VortexEquivalent Latitude Equivalent Latitude
Collar
Extra-VortexSeptember October
EarlyWarming
RecordCold
Ozo
ne
(DU
)Total Ozone: October, Vortex Core
Scatter plot, Detrended Total O3 vs Detrended Temperature (440 K) :
Cold winters associated with larger vortices and less ozone, due to combinationof “dynamical effects” and “chemical effects” related to availability of PSCs
(Boedeker et al., 2002; Newman et al., 2004; Huck et al., 2005)
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
Total Ozone: October, Vortex Core
EarlyWarming
RecordCold
Ozo
ne
(DU
)
Total Ozone: October, Vortex Core
EarlyWarming
RecordCold
Ozo
ne
(DU
)
▪ Have dealt with Complication #1 (Meteorology)
▪ Now, must deal with Complication #2 (Loss Saturation)
Loss Saturation, Method #1 : PDFs of Total Column Ozone
Difference Attributable to Loss Saturation
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
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 )
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 )
Ozonesondes SAGE II
Adjust Total Ozone Time series by 13 DU (mean value of loss saturationfor 1994 to 2006), with coldest years having larger adjustments
Total Ozone: October, Vortex Core
Polar EESC
EarlyWarming
RecordCold
Sept Core
Oct Core
Sept Collar
Oct Collar
Trend Analysis:
CUSUM Analysis: Black: Cumulative Sum of Residuals (i.e., deviation of data from fit)
Sept Core
Oct Core
Sept Collar
Oct Collar Blue dotted: 95% confidence limit
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)