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Xiong Liu ( xliu@cfa.harvard ) Harvard-Smithsonian Center for Astrophysics

Cross-Evaluation of GEOS-CHEM and GOME Tropospheric Column Ozone. Xiong Liu ( xliu@cfa.harvard.edu ) Harvard-Smithsonian Center for Astrophysics

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Xiong Liu ( xliu@cfa.harvard ) Harvard-Smithsonian Center for Astrophysics

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  1. Cross-Evaluation of GEOS-CHEM and GOME Tropospheric Column Ozone Xiong Liu (xliu@cfa.harvard.edu) Harvard-Smithsonian Center for Astrophysics K. Chance, C.E. Sioris, R.J.D. Spurr, T.P. Kurosu, R.V. Martin, M. Fu, J.A. Logan, I. Megretskaia, P.I. Palmer, M.J. Newchurch, D.J. Jacob, R. Chatfield, P.K. Bhartia 2nd GEOS-HCEM Users’ Meeting Harvard University, April 4, 2005

  2. Outline • GOME Tropospheric Column Ozone Retrieval • Tropopause, Sampling GEOS-CHEM data • GOME vs. GEOS-CHEM Tropospheric Column Ozone • Evaluation of both GOME and GEOS-CHEM with MOZAIC and Ozonesonde Observations • Summary

  3. GOME Tropospheric Column Ozone Retrieval • Ozone profile and tropospheric ozone: directly retrieved from GOME Ultraviolet radiance spectra with the LIDORT model • Rodgers’ optimal estimation with v8-TOMS climatological a priori • Wavelength range: 289-307 nm, 326-340 nm • Perform extensive wavelength and radiometric calibrations and improve radiative transfer simulations to reduce the fitting precision to < 0.2% • NCEP/NCAR tropopause: divide the troposphere and stratosphere • Spatial resolution: 960×80 km2 ; Global coverage: 3 days in the equator • Retrieval characterization: • A priori influence: ~15% in the tropics to ~50% at high-latitudes • Precision: ~6% (1.5 DU) in the tropics to ~12% (3 DU) at high-latitudes • Smoothing error: ~12% (3 DU) in the tropics to ~25% (6 DU) at high-latitudes

  4. Tropopause, GEOS-CHEM Sampling and Adjustment • NCEP tropopause: thermal tropopause • ECMWF dynamic tropopause: 2.5 pvu • Global tropopause: minimum between NCEP and dynamic tropopause • GEOS-CHEM: v6.13, 2.5º × 2 º • Different spatial and vertical resolutions • GEOS-CHEM Adjustment • Sampling GEOS-CHEM data • Apply GOME retrieval averaging kernels • Integrate to the same tropopause

  5. GOME vs. GEOS-CHEM

  6. GOME vs. GEOS-CHEM (09/96-08/97) GEOS-CHEM GOME

  7. GOME vs. GEOS-CHEM DJF97 SON96

  8. GOME vs. GEOS-CHEM MAM97 JJA97

  9. GOME vs. GEOS-CHEM • Poor correlation: central America, equatorial remote Pacific, tropical North Africa and Atlantic, North high latitudes • Large positive bias of 6-12 DU: central America, tropical North Africa, Southeast Asia • Comparisons with MOZAIC/ozonesonde: use the same tropopause and surface pressure with correction

  10. Comparison vs. Mozaic/Ozonesonde-Central America

  11. Comparison vs. Mozaic/Ozonesonde-Southeast Asia

  12. Comparison vs. Mozaic/Ozonesonde-N. Africa & Mid East

  13. Comparison vs. Mozaic/Ozonesonde-North Europe

  14. Summary • The overall structures in Tropospheric Column Ozone (TCO) are similar: wave-1 pattern in the tropics and nearly zonally-bands of high TCO at ~30ºN/S. The seasonality is similar at most regions. • GEOS-CHEM TCO is higher than GOME TCO by ~6-12 DU at some tropical regions (e.g., central America, North Africa and North Atlantic, and southeast Asia). Poor correlation occurs at some tropical regions and northern high-latitudes. • Comparisons with MOZAIC and ozonesonde observations show that most of the positive biases over central America and Southeast Asia are from GOES-CHEM TCO except at Paramaribo and Delhi. • GEOS-CHEM better captures the seasonality at North Africa, Dubai, northern Europe, and slightly better at southeast Asia.

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