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)