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Tropospheric Ozone Residual

Tropospheric Ozone Residual. M. Schoeberl NASA/GSFC. Tropospheric Residual Methods. Fishman & Larson [1987, 1990] subtraction of SAGE and TOMS data (probably only works in tropics - stratospheric data very low spatial resolution) Fishman et al. [2003] -

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Tropospheric Ozone Residual

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  1. Tropospheric Ozone Residual M. Schoeberl NASA/GSFC

  2. Tropospheric Residual Methods • Fishman & Larson [1987, 1990] • subtraction of SAGE and TOMS data (probably only works in tropics - stratospheric data very low spatial resolution) • Fishman et al. [2003] - • Subtraction of SBUV and TOMS data (SBUV not sensitive to lower stratospheric ozone - method might work in tropics) • Ziemke et al. [1998] Cloud slicing (on-off clouds - does not need additional instrument) • Hudson, Thompson, others • Tropical climatological stratosphere subtraction from TOMS • Chandra et al. [2003], Ziemke et al. [2006] TOMS - UARS MLS, OMI-Aura MLS with Aura (first attempt at extra-tropics) • Liu et al. [2006] - Direct retrieval of tropospheric ozone from GOME

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

  4. Ziemke et al. [2006] OMI-MLS 6 day average Simply interpolation between MLS tracks, no time synchronization Air pollution transport? 0 ppbv 80 Ziemke et al. 2006 - asynoptic low res. stratosphere

  5. Column Ozone June 28, 2005

  6. Tropopause HeightJune 28, 2005 20 km 5 km

  7. Validation • Ziemke et al. [2006] validated tropospheric residual against monthly mean ozone sondes - validation of his product against daily sondes show poor agreement in the extra tropics. • Validation tends to be sensitive to tropopause height (definitions may vary) • Validation against 200 hPa column eliminates the tropopause definition problem. Trop. avg. mix ratio vs sondes from Ziemke et al. [2006]

  8. Improvement of TOR • Problem 1: Generating a high resolution stratospheric product • MLS or HIRDLS stratospheric data has ~100 times lower spatial resolution than OMI (~15º-25º vs ~0.25º). • Trajectory technique (Schoeberl et al. 2007) • PV- mapping (Yang et al. 2007) • Combination • Problem 2: Time synchronization • Problem 3: Instrument bias - columns from OMI and MLS or HIRDLS don’t agree

  9. Trajectory Generated High Resolution Stratospheric Ozone Column To increase the effective resolution of the MLS (or HIRDLS) data, forward trajectories can mapped from the previous 6 days on to the orbit track. Theoretical Improvement: 6 days of trajectory mapping gives ~ 2-3º horizontal resolution.

  10. PV- vs. Trajectory method mapping lower stratospheric ozone Interpolation between tracks PV- mapping Trajectory mapping Trajectory mapping in the tropics and PV- in the extra-tropics Also see Yang et al. [2007]

  11. 6 day average Ziemke et al. 2006 80 0 ppbv Tropospheric Equivalent Mixing Ratio The high ozone feature off the east coast appears to be a fold - white contours show the tropopause gradient - not pollution. However, the magnitude of the fold tropospheric ozone event is very high….

  12. Improved Time Synchronization The asynoptic assumption - measurement times are ignored. This can create problems with rapid moving events like folds. Synoptic TOR • Use OMI L2G with measurement time stamp • 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 greatly reduced

  13. Time Synchronized Product Tropospheric Column Not Time Synchronized Time Synchronized

  14. Validation of Trajectory Product Schoeberl et al. 2007

  15. Which method does better? Trajectory only Combined Trajectory - PV-

  16. Preliminary test with HIRDLS data HIRDLS v02.04.09 MLS v1.5 Strat column greater than OMI July 3, 2005

  17. HIRDLS O3 Strat column high bias compared to SHADOZ and MLS at high latitudes Hot spots associated with convection. Courtesy of Jacquie Witte

  18. Current Status • All OMI - MLS data processed from Oct-04 to May-07 using PV-/Trajectory mapping • HIRDLS version needs tuning • Combine MLS & HIRDLS? • OMI only strat-column (Liu)

  19. Summary • Trajectory and PV- mapping of MLS data is used to create a high horizontal resolution stratospheric ozone column which is then used with OMI data to produce a daily tropospheric ozone residual (TOR). • Trajectory mapping alone does a reasonable job at mid - latitudes but there is more variability in the product than in sondes • Folds dominate the trop column at high latitudes • Time synchronization cannot be neglected • Anybody can do the tropics reasonably well • HIRDLS data seem to work well in generating TOR using the same method • Some evidence of high bias for HIRDLS column at high latitudes • Tropical hot spots are very annoying

  20. Seasonal TOR Mixing Ratio March - May Dec. - Feb. Sept. - Nov. June - Aug.

  21. Zonal Mean Variations 2005 J J

  22. The End

  23. Comparison to GMI Combo Jan 6, 2005

  24. Column Ozone vs Average Column Mixing Ratio Sept-Aug‘05 Trop. Column Ozone and Average Mixing Ratio ppbv DU (HTOR)

  25. 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.

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