1. Daily Tropospheric Ozone Residual from OMI-MLS
M. Schoeberl, J. Ziemke, P. K. Bhartia, B. Bojkov, A. Douglass,
B. Duncan & GMI Team & Ozonesonde groups
NASA/GSFC
L. Froidevaux, N. Livesey, J. Waters
JPL
P. Levelt
KNMI, Netherlands

2. Tropospheric Ozone Residual (TOR)
MLS Stratospheric O3 Column Map made from MLS measurement points shown
How hard can it be to subtract two numbers?

3. Increasing the Resolution of the Stratospheric Column with
Forward trajectories from six previous days of MLS V1.5 data are used to increase the stratospheric column resolution
OMI L2G with measurement time stamps are used to correct for asynoptic affects
Forward trajectories are grouped in time for target day (1/10th day resolution)
Tropopause is time interpolated from 6 hour DAS fields
Product has same zonal mean as asynoptic TOR
Fold TOR anomalies are better handled
June
MLS Ascending node measurements
Forward Trajectory Points

4. Time Synchronized Product
Tropospheric Column
Not Time Synchronized
Time Synchronized

5. Column Ozone vs Average Column Mixing Ratio
Sept-Aug‘05 Trop. Column Ozone and Average Mixing Ratio DU
ppbv
(HTOR)
The tropospheric equivalent mixing ratio tends to reduce the topographic effects.

6. Seasonal Tropospheric O3 Mixing Ratio
Dec. - Feb.
March - May
June - Aug.
Sept. - Nov.

7. Validation Sonde Comparisons TES Comparisons
Ziemke product Comparisons
Most comparisons are made using the surface-200hPa product from sondes and TES - this avoids issues with different definitions of the tropopause.
Dates: October 2004 to December 31, 2006
Data is interpolated to location of sonde or TES measurement.
Sonde data base >6000 comparisons from Envisat, Shadoz, Canadian,
IONS,etc.

8. 2.4 DU offset (sondes larger)
Tropical Sondes
690 sondes
2.4 DU offset (sondes larger)

9. 3.4 DU offset (sondes larger)
Mid-latitude Sondes
June -July- August
688 sondes
3.4 DU offset (sondes larger)
Wider pdf

10. 2.9 DU offset (sondes larger)
Mid-latitude Sondes
March-April-May
462 sondes
2.9 DU offset (sondes larger)
Even wider pdf

11. TES Comparison Tropics
4.1 DU offset (TES larger)
For sondes the ST DEV was 5.4 DU

12. TES Comparison at Mid-Latitudes
3.4 DU offset (TES larger)
For sondes the ST DEV was 8.7 DU

13. Validation Summary

14. For sondes the ST DEV was 5.4 DU
Z06 Comparison Tropics
2.3 DU offset
For sondes the ST DEV was 5.4 DU

15. For tropics the ST DEV was 4.2 DU
Z06 Comparison April
-7.7 DU offset
For tropics the ST DEV was 4.2 DU

16. Comparison to GMI Combo Jan 6, 2005

17. Seasonal Variations (2005)
Extra-tropical (tropical) region is defined as region where the tropopause is below (above) 12 km. The mass is normalized to the annual averaged area occupied by the respective regions.

18. Zonal Mean Comparison with GMI
Overall good agreement
Arrows indicate some differences:
GMI SH and NH mid-latitude maxima starts sooner
OMI-MLS values too low at high latitudes
Winter tropical values are lower than GMI

19. PDF Comparison with GMI
No longer surf -200 hPa column

20. Summary
Forward Trajectory transport of MLS data is used to create a high horizontal resolution stratospheric ozone column which is then used to produce an improved tropospheric ozone residual (TOR).
Fold events appear to dominate TOR day-to-day extra-tropics, but using better time synchronization, fold event amplitudes are greatly reduced.
Validation with sondes shows good tropical comparisons, but more variability in TOR at mid-latitudes than sondes
TES comparisons show similar results
Both TES and Sondes show a systematic offset with OMI-MLS being a few DU low
Comparisons of total tropospheric ozone amount to GMI Combo model show overall good agreement
Differences in extra-tropics may be due to more vigorous circulation in GMI
Differences in tropics due to different emissions and convection

21. Questions
Why is there more variability in the TOR than in the GMI or sondes or TES?
Clue: variability is associated with folds - or strong vertical changes
Clue: both enhancements and depletions are larger
Clue: independent of tropopause definition
Clue: TOR is systematically low - this bias is larger at mid-latitudes
One explanation that fits all these data is that the ozone amount at 215 hPa is too large or too variable - stratospheric ozone variability is miss-assigned to the troposphere
Consistent with data presented by Froidevaux et al. [2006], Livesey et al. [2007]
More variation in TOR
Less variation in TOR
X - >
X - >

22. Now I will make some rambling semi-coherent remarks…
V2.2 vs V1.5
GEOS Chem vs MLS
Livesey et al. [2007]