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Validation of OMI Ozone Profiles and Tropospheric Ozone Retrievals

This study validates OMI ozone profile retrieval method and compares tropospheric ozone data with MLS and ozonesonde measurements. Results show strong agreement for stratospheric ozone, with seasonal and latitudinal biases in tropospheric ozone.

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Validation of OMI Ozone Profiles and Tropospheric Ozone Retrievals

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  1. Validation of OMI Ozone Profile and Tropospheric Ozone Retrievals Xiong Liu1,2,3, Pawan K. Bhartia3, Kelly Chance2, Thomas P. Kurosu2, B.R. Bojkov1,3, Robert J.D. Spurr4, Ozonesonde Investigators xliu@umbc.edu 1Goddard Earth Sciences and Technology Center,UMBC 2Harvard-Smithsonian Center for Astrophysics 3NASA Goddard Space Flight center 4RT Solutions Inc. OMI Science Team Meeting June 25, 2008

  2. Outline • Introduction • Comparison with OMTO3 and OMDOAO3 • Comparison of OMI ozone profiles and stratospheric ozone columns with MLS data • Comparison of OMI ozone profiles and tropospheric ozone columns with ozonesonde data • Examples of retrieved tropospheric ozone • Summary and future work

  3. Introduction • OMI ozone profile retrieval (Liu et al., 2005) • Retrieve ozone at 24 ~2.5-kmthick layers from 270-330 nm radiances • Optimal estimation technique • Use ozone profile climatology by Mcpeters et al. (2007) to constrain retrievals • Apply X-track and wavelength-dependent correction (assuming multiplicative) derived from 1 day’s zonal mean MLS in the tropics • DFS: 5-8 in the atmosphere with up to 2 in the troposphere. • Vertical resolution: ~6-8 km FWHM in the stratosphere and ~8-15 km in the troposphere

  4. Introduction 2006m0615 • Information content in the first 0-3 km layer • DFS: 0.15-0.4 for most of the latitude range (i.e., 15-40% of ozone deviated from a priori can be retrieved at this layer) • 40-80% of ozone deviated from a priori can be captured in the retrievals

  5. Random (N) and Smoothing (S) Errors • N: <~2% above 22 km and within ~10% below • S+N: within 3% between 22-40 km, increase to 10% above 40 km, and to 15-30% below 20 km. • SOC: 0.5-2 DU (N), 1.5-4 DU (S+N) • TOC: 0.8-3 DU (N), 1.5-6 DU (S+N) • TOZ: 0.2-3 DU (N), 0.5-6 DU (S+N)

  6. Larger biases at high SZA 2006m0110 2006m0501 2006m0711 2006m0502 Comparison with OMTO3and OMDOAO3 OMTO3: 2.5-3.3 ± 3.3-4.7 DU ( 0.9-1.1± 1.1-1.5%) OMDAO3: -1.2-3.3 ± 4.2-6.7 DU (-0.3-1.1± 1.4-2.1%) • Comparison for 12 days in 2006

  7. Without OMI AKs With OMI AKs Comparison with MLS Ozone Profiles • MLS: on-board EOS-AURA, spatiotemporally coincident with OMI • MLS O3 error estimate:~5% in the upper strat., ~10-15% in the lower strat., ~2-3% in strat. O3 column (Froidevaux et al., 2007)

  8. Comparison with MLS Ozone Profiles Without OMI AKs With OMI AKs Mean biases and standard deviations are within ~5% between 2-50 mb.

  9. Comp. with MLS 215 hPa O3 Column 15 days of Comparison Mean Bias: -0.5-1% Std. Dev. (Global): 2.4-2.9% Std. Dev. (Tropics): 1.8-2.6% 0-200 hPa O3 columns can be accurately derived from OMI !!!

  10. Comp. with MLS 215 hPa O3 Column 2006m0110 2006m0501 2006m0711 2006m1015

  11. Comparison with Ozonesondes • Ozonesonde data: available at AURA AVDC for August 2004-March 12, 2007 • For consistency, all ozonesonde data are not normalized to coincident total ozone column • Coincidence criteria: within 6 hours, 1º longitude & latitude, OMI edge pixels excluded • Focus on two latitude bands: Tropics (30ºS-30ºN), Northern Mid- Latitudes (30ºN-60ºN) • Compare profile and tropospheric O3 column (surface-200 mb) • Ozonesonde profiles are convolved with OMI averaging kernels, but not the tropospheric ozone column

  12. Comparison with Ozonesondes (30ºS-30ºN) • Profile: within 15%, significant improvement throughout the troposphere Solid line: mean Dashed line: 1 • Tropospheric Ozone column (Surface-200 mb): –4.65.6 DU, high correlation (0.8)

  13. Spring Winter Summer Fall Comparison with Ozonesondes (30ºN-60ºN) • Within 10-20%, significant improvement in the middle and upper troposphere.

  14. Comparison with Ozonesondes (30ºN-60ºN) • Northern Midlatitudes (30ºN-60ºN) • Winter: 2.39.2 DU, R = 0.58 • Spring: 1.88.7 DU, R = 0.74 • Summer: -5.66.4 DU, R = 0.79 • Fall: 0.75.6 DU, R = 0.51 Seasonal/latitudinal dependent biases Not from vertical resolution & radiative transfer approximation

  15. “Boundary ozone” (0-3 km) Ozone over Southeast Asia • Enhanced ozone over Indonesia in Oct. 2006 relative to Oct. 2005. • Enhanced ozone over South China especially in Oct. 2006.

  16. Column-Averaged O3 Mixing Ratio (July 15 – September 7, 2006)

  17. Summary • Ozone profiles and tropospheric ozone are retrieved from OMI radiances. Stratospheric and tropospheric ozone columns can be very well derived from OMI data alone. • OMI ozone profiles and stratospheric ozone columns compare well with MLS, to within combined retrieval uncertainties. • OMI ozone profiles and tropospheric ozone columns compare well with ozonesonde data, but show seasonal and latitude-dependent biases. • Retrievals show signals due to pollution, biomass burning, regional and intercontinental transport, convection, and stratospheric influence.

  18. Future Work • Better understand biases with respect to other correlative measurements and continue to improve retrieval algorithm • Speed up retrieval algorithm with specialized VLIDORT or linearized TOMRAD (Dave Flittner). • Make data available for the whole OMI record. • Interpret retrievals using CTMs, meteorology, in-situ and other satellite data. • Acknowledgements • OMI and MLS Science Teams • Support from NASA • Support from various organizations on Ozonesonde observations

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