# Presentation: 024037

## Stratospheric Ozone : Depletion and Recovery

- Ross J. Salawitch1, Eun-Su Yang2, Michael J. Newchurch2, Derek Cunnold3,
- James Russell III4, M. Patrick McCormick4, Joseph Zawodny5, Sam Oltmans6
- 1 Univ of Md, 2 Univ of Ala, Huntsville, 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 ?**

**TOMS**

**OMI**

**Ground Based**

- Motivation:

## Complication #1

**Large year to year variability**
**in temperature**

## 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**

## WMO 2006 (Chapter 6) Definition,  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**

## 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)

**Vortex**

**Equivalent Latitude**

**Equivalent Latitude**

**Collar**

## Total Ozone in Vortex Core, October

**Scatter plot, Detrended O****3**** vs Detrended Temperature (70 hPa) :**

**Ozone (DU)**

## Scatter plot, Detrended Total O3 vs Detrended Temperature (440 K) :

**Cold winters associated with larger vortices and less ozone, due to combination**
**of “dyamical effects” and “chemical effects” related to availability of PSCs**
**(Boedeker et al., 2002; Newman et al., 2004)**

## 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

**Early**
**Warming**

**Record**
**Cold**

## Total Ozone: October, Vortex Core

**Early**
**Warming**

**Record**
**Cold**

**▪ ****Have dealt with Complication #1 (Meteorology)**
**▪ ****Now, must deal with Complication #2 (Loss Saturation)**

**WMO 2006**
**Polar EESC**
**(Mean age: 6 yrs**
**Width: 3 yrs**
**Alpha:  65 )**

## Loss Saturation, Method #1 : PDFs of Ozone

**Difference Attributable to**
** ****Loss Saturation**

**October vortex core:  mean ozone is 15 DU higher (1997 to 2006) than “predicted ozone”**
**                                     ****found using T residuals and slope from 1979 to 1996 time period**
**October vortex collar: 13 DU effect**
**September core and collar: no discernable saturation effect**

## Loss Saturation, Method #2 : 

-         (O3) vs (T)

**October vortex core:  ozonesonde saturation effect : 8.9 DU (1.2 + 4.0 + 3.7)**
**                                     ****SAGE II saturation effect:        15.4 DU (4.1 + 5.4 + 5.9 )**

**Ozonesondes**

**SAGE II**

## Loss Saturation, Method #2 : 

-         (O3) vs (T)

**Ozonesondes**

**SAGE II**

**Adjust October core (collar) ozone time series by mean values of 15 DU (13 DU)**
**for 1997 to 2006, with coldest years having larger adjustments**

**October vortex core:  ozonesonde saturation effect : 8.9 DU (1.2 + 4.0 + 3.7)**
**                                     ****SAGE II saturation effect:        15.4 DU (4.1 + 5.4 + 5.9 )**

## Total Ozone: October, Vortex Core

**Early**
**Warming**

**Record**
**Cold**

**WMO 2006**
**Polar EESC**
**(Mean age: 6 yrs**
**Width: 3 yrs**
**Alpha:  65 )**

## Trend Analysis:

**Deviation from **
**1979 to 1996 trend**

## CUSUM Analysis:

**Deviations are**
**Statistically Significant**
**(blue dotted: 95% confidence limit)**

## Conclude:

-    ▪ **Antarctic Ozone**, within *both core and collar region*,
-      is in the **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 now driven by meteorology**
-    ▪ **Cold winters ******** low ozone**
-         Next project: attribution of changes upper stratospheric ozone
-         using Aura/UARS MLS ClO, UARS HALOE CH4, Aura MLS N2O,
-         and UARS HALOE HCl and Aura MLS HCl

## Backup Material

## Slide 19

## Slide 20

## Solomon et al., JGR, 2005