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1 Cross Evaluation of OMI, TES, and GEOS-Chem Tropospheric Ozone Xiong Liu 1, Lin Zhang 2, Kelly Chance 1, John R. Worden 3, Kevin W. Bowman 3, Thomas.

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Presentation on theme: "1 Cross Evaluation of OMI, TES, and GEOS-Chem Tropospheric Ozone Xiong Liu 1, Lin Zhang 2, Kelly Chance 1, John R. Worden 3, Kevin W. Bowman 3, Thomas."— Presentation transcript:

1 1 Cross Evaluation of OMI, TES, and GEOS-Chem Tropospheric Ozone Xiong Liu 1, Lin Zhang 2, Kelly Chance 1, John R. Worden 3, Kevin W. Bowman 3, Thomas P. Kurosu 1, Daniel J. Jacob 2 1 Harvard-Smithsonian Center for Astrophysics 2 Harvard University 3 Jet Propulsion Laboratory 3 rd GEOS-Chem Users’ Meeting 2007 Harvard University April 11, 2007

2 2 Outline nMotivation nTES retrievals and GEOS-Chem simulation nPreliminary OMI ozone profile retrievals nComparison methodology nOMI/TES/GEOS-Chem comparison nSummary

3 3 Motivation n OMI/TES: both on EOS-AURA and measure tropospheric ozone uOMI: ~10-12 km FWHM in the troposphere, 13×24 km 2, global coverage uTES: ~6 km FWHM in the troposphere, 5×8 km 2 Worden et al., 2007 nTropospheric ozone retrievals can be greatly improved with joint UV/IR retrievals [Worden et al., 2007]. nAre OMI/TES data consistent? nHow well does GEOS-Chem simulation compare with OMI/TES ozone?

4 4 TES Retrievals and GEOS-Chem Simulation nTES: V 2.0 u Compares well with ozonesonde observations: generally biased higher by ~10% [Ray et al., 2007]. u 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]. nGEOS-Chem simulation: V7-04-09 with GEOS-4 u Lightning NOx: 6 Tg/yr, rescaled with OTD/LIS climatology u Increase Chinese NOx emission by ~70% (2006)

5 5 (a) Preliminary OMI Ozone Profile Retrievals nOMI retrievals: O 3 at 24 ~2.5 km layers with optimal estimation uFitting window: 270-310 nm (UV-1), 310-330 nm, 368-372 nm (UV-2) uO 3 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 (b)

6 6 (a) May 8, 2006 (a)Original (b)Soft calib. (c)Soft calib. +destriping (d)A Priori (e)600 mb f c < 0.3 Preliminary OMI Ozone Profile Retrievals (b) nOMI calibration: wavelength and cross-track dependent errors u Derive soft correction (, , multiplicative) by simulating OMI radiances: McPeters (strat.) and Logan (1999) trop. O 3 clima. Assumption: climatology represents ozone fields on global average u Remove remaining systematic stripes (c) (d) (e)

7 7 Comparison Methodology nOMI/TES retrievals: different retrieval grid and a priori u Relatively coarser vertical resolution (vs. ozonesonde) u TES: more tropospheric ozone information (two defined peaks) u OMI: more stratospheric ozone information Examples of coincident clear-sky AKs (a) TES (67 levels) (b) OMI (24 layers) 15°N40°N60°N

8 8 Comparison Methodology nUse GEOS-Chem as an intermediate, also evaluate GEOS-Chem: uInterpolate GEOS-Chem/TES to OMI grid (coarsest) uAppend GEOS-Chem with TES stratospheric ozone uCompare GEOS-CEHM with TES (TES AKs + OMI a priori) uCompare GEOS-CEHM with OMI (OMI AKs + OMI a priori) nCompare OMI/TES directly, similar to Luo et al. [2007]: uInterpolate TES to OMI grid and adjust TES with OMI a priori uApply OMI AKs to TES data nCompare OMI/TES with ozonesonde observation later (not here) nPresent the comparison on May 08, 2006 (similar on other days) uRemove poor retrievals (i.e., TES master flag, emission layer flag, OMI fitting residuals) and cloudy pixels (OMI f c > 0.3) u 550 coincidences

9 9 OMI/TES/GEOS-Chem TCO on May 8, 2006 Generally consistent spatial distribution despite systematic biases

10 10 OMI/TES/GEOS-Chem TCO on May 8, 2006 MB = -8%MB = -6% MB = -7%MB = 4%

11 11 OMI/TES/GEOS-Chem Comparison (a)Difference due to OMI/TES AKs can be up to 10-15% especially in UT (b)Large negative (10°N-20°N, high sun) and positive (40°S-25°S, low sun) biases may be caused by non-linearity of the OMI calibration. (a) (b) Mainly systematic OMI/TES differences

12 12 OMI/TES Comparison (b) Those biases are not caused by a priori (a, c, d) Mostly systematic differences a bcd

13 13 Summary nThe spatial distribution of OMI, TES, and GEOS-Chem tropospheric ozone is similar on the global scale. nTES shows a systematic positive bias of ~10% relative to GEOS- Chem. nOMI shows a negative bias of ~15% relative to TES except for 10°N-20°N (~ -30%) and 45°S-25°S (~20%). The large negative bias at high sun and positive bias at low sun may be related to the non-linearity calibration of OMI. nOMI/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

14 14 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

15 15 OMI TCO (North Pacific on May 05-10, 2006) OMI tropospheric column ozone f c < 0.3 Gridded to 2.5°×2°

16 16 Persistent high O 3 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 OMI/TES/GEOS-Chem Ozone (600 mb) on May 04-12, 06 05/04 05/06 05/08 05/10 05/12

17 17 Append GEOS-Chem with TES stratospheric ozone How does the Appending of Different Stratospheric Ozone to GEOS-Chem Affect the Comparison? Append GEOS-Chem with OMI a Priori stratospheric ozone


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