NASA/GSFC Tropospheric Ozone Residual M. Schoeberl NASA/GSFC 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] - –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 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

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

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

NASA/GSFC Column Ozone June 28, 2005

NASA/GSFC Tropopause Height June 28, km 5 km

NASA/GSFC 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. 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]

NASA/GSFC 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 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

NASA/GSFC 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.

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

NASA/GSFC 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…. 6 day average Ziemke et al ppbv

NASA/GSFC 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 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

NASA/GSFC Time Synchronized Product Time Synchronized Tropospheric Column Not Time Synchronized

NASA/GSFC Validation of Trajectory Product Schoeberl et al. 2007

NASA/GSFC Which method does better? Trajectory only Combined Trajectory - PV- 

NASA/GSFC Preliminary test with HIRDLS data HIRDLS v MLS v1.5 Strat column greater than OMI July 3, 2005

NASA/GSFC HIRDLS O 3 Strat column high bias compared to SHADOZ and MLS at high latitudes Hot spots associated with convection. Courtesy of Jacquie Witte

NASA/GSFC 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) 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)

NASA/GSFC 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 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

NASA/GSFC Seasonal TOR Mixing Ratio Dec. - Feb. June - Aug. Sept. - Nov. March - May

NASA/GSFC Zonal Mean Variations 2005 J J

NASA/GSFC The End

NASA/GSFC Comparison to GMI Combo Jan 6, 2005

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

NASA/GSFC 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.