# Presentation: 854631

## Estimate of Stratosphere-Troposphere Exchange of Ozone Derived From MLS Observations Mark A. Olsen1, Mark R. Schoeberl2, and Jerry R. Ziemke11GEST/NASA Goddard Space Flight Center2NASA Goddard Space Flight CenterCorrespondence:  olsen@code613-3.gsfc.nasa.gov

**Introduction**
- Daily high-resolution maps of stratospheric ozone have been constructed using observations by MLS combined with trajectory information.  We have estimated the extratropical stratosphere-troposphere exchange (STE) of ozone for the year 2005 with two different diagnostic methods using the high-resolution maps.  The resulting annual estimates and seasonal characteristics are compared with prior studies.  A high-resolution tropospheric ozone product is created by subtracting this MLS stratospheric ozone from OMI column measurements.  The locations of the ozone STE are compared with the tropospheric ozone maps to determine the impact of the cross-tropopause transport on the tropospheric composition.

**STE Diagnostics**
-   Mass (M) balance of fluxes (F) into and out of lowermost stratosphere.
-   380 K flux determined from heating rate on surface (here from UKMO fields).
-   Ozone mixing ratio is convolved with mass flux at 380 K to determine tropopause flux (assume no net source or sink in lowermost stratosphere).
-   Back trajectories of 3-D (here 30°-60°) grid of parcels used to determine PV of parcels one day prior.  Pv values are mapped to parcel position at analysis time.
-   Difference in tropopause height in analysis and “conserved PV” fields indicates STE.
-   Ozone STE determined by amount of ozone between analysis and “conserved PV” tropopauses.

**STE Estimates**
-   STE estimates from this study are consistent with previous studies given interannual variability and possible trends.
-   PV-Trajectory method estimates only for mid-latitudes.  Results are 74% and 82% of extra-tropical results of mass balance method in the NH and SH, respectively.
-       NH STE Seasonal Cycle
-       SH STE Seasonal Cycle
-   Minimum values in both hemispheres are similar with both methods.  Mass balance method results in greater maxima in both hemispheres.  This implies that a significant amount of ozone STE occurs in the polar region only during the Spring and early Summer.
-   Rapid decline in ozone STE in the SH using the mass balance method occurring near the end of September.  This rapid decrease not seen in the mass balance results of Olsen et al. [2004] that used 1979-1983 source gas boundary conditions with GEOS-4 meteorological fields.  This suggests the SH polar ozone destruction as a cause or a difference between the heating rate fields used in the studies.
-    The lack of such a rapid decline in the PV-Trajectory method results is consistent with the ozone hole as the cause since this method calculated the transport from 30°-60° only.

**Tropospheric Ozone and Relationship to STE**
- Color contours are the mean tropospheric ozone mixing ratio to remove topographic influence.  White contours are the ozone STE from the PV-Trajectory method (contour interval is 2x108 g beginning at 2x108 g).  Results from grid points with high reflectivity, low tropopause (3.5 PVU), etc. are flagged and appear as black.
-   Both TOR methods agree on general location of tropospheric maxima.
-   The HTOR tends to exhibit greater horizontal structure as expected.
-   The tropospheric ozone maxima tend to be associated with tropopause folds (as described in Schoeberl plenary talk, not shown here).
-   The tropospheric ozone maxima also tend to occur with or near locations of significant ozone STE.

**Summary and Conclusions**
-   Both ozone STE methods using the MLS trajectory-based high resolution maps produce reasonable annual estimates.  The results compare well with previous model and empirical estimates.
-   Comparison of the two STE methods indicate that significant ozone STE occurs in the polar region only during Spring and early Summer.
-   The Antarctic ozone hole is indicated as responsible for a rapid decrease in SH ozone STE near the beginning of October.  This will be investigated further in future work.
-   The mean tropospheric ozone maxima calculated by subtracting the high-resolution MLS fields from the OMI total column data tend to occur near locations of significant ozone STE.  Thus, ozone STE may be responsible for a significant fraction of any mean tropospheric ozone anomaly.
-   However, not all STE maxima are associated with maxima in the tropospheric ozone field.  This also requires further investigation.

- [Appenzeller et al. 1996]

**High-Resolution Ozone Maps**
- MLS data from day of interest + data from each of previous six days mapped by forward trajectory.   (Presented in Tuesday plenary talk by Mark Schoeberl).
-   Results interpolated to 1° x 1.25° grid.

- Mass Balance Method
- [Olsen et al. 2004]

- PV-Trajectory Method
- [Olsen et al. 2003]

**EQ**

- 380 K

- Tropopause

- M

- F

- F

**NP**

**F****trop**** ****=**** ****F****380K**** ****+**** ****dM/dt**

- Tropopause = 3.5 PVU

| Tg/yr | Mass Bal.
(This Study) Year 2005 | PV-Traj.
(This Study) Year 2005     (30°-60°) | Olsen et al., 2003
(PV-Traj.) Year 2000     (30°-60°) | Gettleman et al., 1997      4-Year Mean
1992-1995 | Olsen et al., 2004
(Mass Bal.)    5-Year Mean  1979-1983 Boundary Conditions | Roelofs and Lelieveld, 1995 |
| --- | --- | --- | --- | --- | --- | --- |
| NH | 350 | 260 | 260 | 290 | 250 | 340 |
| SH | 230 | 190 | 210 | 220 | 250 | 230 |

- ----Model-based----

- ----Observation-based----

- Mass Bal.

- Mass Bal.

- PV-Traj.

- PV-Traj.

- High-resolution tropospheric ozone residual (HTOR)

- Ziemke TOR (no forward-trajectory mapping of MLS data)
- [Ziemke et al., J. Geophys. Res., in press, 2006]

- June 26, 2005

- June 28, 2005

- July 1, 2005

- June 28, 2005

- References:
- Appenzeller, C., J. R. Holton, and K. H. Rosenlof (1996), Seasonal variation of mass transport across the tropopause, *J. Geophys. Res., 101,* 15071-15078.
- Gettelman, A., J. R. Holton, and K. H. Rosenlof (1997), Mass fluxes of O3, CH4, N2O and CF2Cl2 in the lower stratosphere calculated from observational data, *J. Geophys. Res., 102,* 19149-19159.
- Olsen, M. A., A. R. Douglass, and M. R. Schoeberl (2003), A comparison of Northern and Southern Hemisphere cross-tropopause ozone flux, *Geophys. Res. Lett., 30*(7), 1412, doi:10.1029/2002GL016538.
- Olsen, M. A., M. R. Schoeberl, and A. R. Douglass (2004), Stratosphere-troposphere exchange of mass and ozone, *J. Geophys. Res., 109, *D24114, doi:10.1029/2004JD005186.
- Roelofs, G.-J., and J. Lelieveld (1995), Distribution and budget of O3 in the troposphere calculated with a chemistry general circulation model, *J. Geophys. Res., 100,* 20983-20998.

- Note:  negative sign convention is net stratosphere to troposphere transport.