Cross Evaluation of OMI, TES, and GEOSChem Tropospheric Ozone

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Cross Evaluation of OMI, TES, and GEOS-Chem
Tropospheric Ozone

• Xiong Liu1, Lin Zhang2, Kelly Chance1, John R.
  Worden3, Kevin W. Bowman3, Thomas P. Kurosu1,
  Daniel J. Jacob2
• 1 Harvard-Smithsonian Center for Astrophysics
• 2 Harvard University
• 3 Jet Propulsion Laboratory
• 3rd GEOS-Chem Users Meeting 2007
• Harvard University
• April 11, 2007

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Outline

• Motivation
• TES retrievals and GEOS-Chem simulation
• Preliminary OMI ozone profile retrievals
• Comparison methodology
• OMI/TES/GEOS-Chem comparison
• Summary

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Motivation

• OMI/TES both on EOS-AURA and measure
  tropospheric ozone
• OMI 10-12 km FWHM in the troposphere, 1324
  km2, global coverage
• TES 6 km FWHM in the troposphere, 58 km2

• Tropospheric ozone retrievals can be greatly
  improved with joint UV/IR retrievals Worden et
  al., 2007.
• Are OMI/TES data consistent?
• How well does GEOS-Chem simulation compare with
  OMI/TES ozone?

Worden et al., 2007
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TES Retrievals and GEOS-Chem Simulation

• TES V 2.0
• Compares well with ozonesonde observations
  generally biased higher by 10 Ray et al.,
  2007.
• Compares well with DIAL obtained during the
  INTEX-B Positive bias of 5-15 and a negative
  biases of up to 20 in the upper troposphere
  Richard et al., 2007.
• GEOS-Chem simulation V7-04-09 with GEOS-4
• Lightning NOx 6 Tg/yr, rescaled with OTD/LIS
  climatology
• Increase Chinese NOx emission by 70 (2006)

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Preliminary OMI Ozone Profile Retrievals

• OMI retrievals O3 at 24 2.5 km layers with
  optimal estimation
• Fitting window 270-310 nm (UV-1), 310-330 nm,
  368-372 nm (UV-2)
• O3 climatology (month, lat, Z) McPeters et al.,
  2007 as a priori

May 8 2006 Overpass US Partial Column Ozone
(DU) (a) Retrieval (b) A priori
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Preliminary OMI Ozone Profile Retrievals

• OMI calibration wavelength and cross-track
  dependent errors
• Derive soft correction (?, ?, multiplicative) by
  simulating OMI radiances McPeters (strat.) and
  Logan (1999) trop. O3 clima.
• Assumption climatology represents ozone
  fields on global average
• Remove remaining systematic stripes

• May 8, 2006
• Original
• Soft calib.
• Soft calib. destriping
• A Priori
• 600 mb
• fc lt 0.3

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Comparison Methodology

• OMI/TES retrievals different retrieval grid and
  a priori
• Relatively coarser vertical resolution (vs.
  ozonesonde)
• TES more tropospheric ozone information (two
  defined peaks)
• OMI more stratospheric ozone information

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Comparison Methodology

• Use GEOS-Chem as an intermediate, also evaluate
  GEOS-Chem
• Interpolate GEOS-Chem/TES to OMI grid (coarsest)
• Append GEOS-Chem with TES stratospheric ozone
• Compare GEOS-CEHM with TES (TES AKs OMI a
  priori)
• Compare GEOS-CEHM with OMI (OMI AKs OMI a
  priori)
• Compare OMI/TES directly, similar to Luo et al.
  2007
• Interpolate TES to OMI grid and adjust TES with
  OMI a priori
• Apply OMI AKs to TES data
• Compare OMI/TES with ozonesonde observation later
  (not here)
• Present the comparison on May 08, 2006 (similar
  on other days)
• Remove poor retrievals (i.e., TES master flag,
  emission layer flag, OMI fitting residuals) and
  cloudy pixels (OMI fc gt 0.3)
• 550 coincidences

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OMI/TES/GEOS-Chem TCO on May 8, 2006
Generally consistent spatial distribution despite
systematic biases
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OMI/TES/GEOS-Chem TCO on May 8, 2006
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OMI/TES/GEOS-Chem Comparison
Mainly systematic OMI/TES differences

• Difference due to OMI/TES AKs can be up to 10-15
  especially in UT
• Large negative (10N-20N, high sun) and positive
  (40S-25S, low sun) biases may be caused by
  non-linearity of the OMI calibration.

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OMI/TES Comparison
(b) Those biases are not caused by a priori (a,
c, d) Mostly systematic differences
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Summary

• The spatial distribution of OMI, TES, and
  GEOS-Chem tropospheric ozone is similar on the
  global scale.
• TES shows a systematic positive bias of 10
  relative to GEOS-Chem.
• OMI shows a negative bias of 15 relative to TES
  except for 10N-20N ( -30) and 45S-25S
  (20). The large negative bias at high sun and
  positive bias at low sun may be related to the
  non-linearity calibration of OMI.
• OMI/TES differences cannot be explained by a
  priori and different averaging kernels, and are
  mainly systematic.
• Acknowledgements
• OMI and TES science team, GEOS-Chem community
• NASA and Smithsonian Institution

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OMI/TES/GEOS-Chem Ozone (600 mb)(North Pacific
during INTEX-B, May 05-09, 2006)
05/05 05/06 05/07 05/08 05/09
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OMI TCO (North Pacific on May 05-10, 2006)
OMI tropospheric column ozone fc lt 0.3 Gridded
to 2.52
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OMI/TES/GEOS-Chem Ozone (600 mb) on May 04-12, 06
05/04 05/06 05/08 05/10 05/12
Persistent high O3 over Northern India from OMI,
not clear from TES, not shown in GEOS-Chem. Maybe
be due to OMI retrieval artifacts (a) absorbing
aerosols (b) incorrect terrain height
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How does the Appending of Different Stratospheric
Ozone to GEOS-Chem Affect the Comparison?
Append GEOS-Chem with OMI a Priori stratospheric
ozone
Append GEOS-Chem with TES stratospheric ozone