NASA/GSFC

Tropospheric Ozone ResidualTropospheric Ozone Residual

M. Schoeberl

NASA/GSFC

M. Schoeberl

NASA/GSFC

NASA/GSFC

Tropospheric Residual MethodsTropospheric 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)Tropospheric Ozone Residual (TOR)

MLS Stratospheric O3 Column Map made from MLS measurement points shown

How hard can it be to subtract two numbers?

NASA/GSFC

Ziemke et al. [2006] OMI-MLSZiemke et al. [2006] OMI-MLS

Ziemke et al. 2006 - asynoptic low res. stratosphere

800 ppbv

Air pollution transport?

Simply interpolation between MLS tracks, no time synchronization

6 day average

NASA/GSFC

Column Ozone June 28, 2005Column Ozone June 28, 2005

NASA/GSFC

Tropopause HeightJune 28, 2005

20 km

5 km

NASA/GSFC

ValidationValidation• 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 TORImprovement 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

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.

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

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. 2006

800 ppbv

NASA/GSFC

Improved Time SynchronizationImproved Time SynchronizationThe 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

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• 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

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• Product has same zonal mean as asynoptic TOR

• Fold TOR anomalies are greatly reduced

NASA/GSFC

Time Synchronized ProductTime Synchronized Product

Time Synchronized

Tropospheric Column

Not Time Synchronized

NASA/GSFC

Validation of Trajectory ProductValidation of Trajectory Product

NH Extratropics Comparison Tropics

DJF MAM JJA SON

Biases (DU) 2.4 3.9 2.9 3.4 5.4

Std. Deviation 5.4 12 13 8.7 8.7 Ozonesonde

Correlation

Coef.

0.73 0.45 0.66 0.68 0.48

Biases 4.1 2.6 0.85 3.4 7.5

Standard

Deviation

6.1 8.2 15 9.8 8.6

TES

Correlation

Coef.

0.72 0.6 0.48 0.54 0.43

Schoeberl et al. 2007

NASA/GSFC

Which method does better?Which method does better?Trajectory only Combined Trajectory - PV-

NASA/GSFC

Preliminary test with HIRDLS dataPreliminary test with HIRDLS data

HIRDLS v02.04.09 MLS v1.5Strat column greater than OMI

July 3, 2005

NASA/GSFC

HIRDLS O3HIRDLS O3Strat column high bias compared to SHADOZ and MLS at high latitudes

Hot spots associated with convection.

Courtesy of Jacquie Witte

NASA/GSFC

Current StatusCurrent 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

SummarySummary• 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.Dec. - Feb.

June - Aug.June - Aug. Sept. - Nov.Sept. - Nov.

March - MayMarch - May

NASA/GSFC

Zonal Mean VariationsZonal Mean Variations2005

J

J

NASA/GSFC

The EndThe End

NASA/GSFC

Comparison to GMI Combo Jan 6, 2005

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)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.