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’ MeetingHarvard University, April 4, 2005

Cross-Evaluation of GEOS-CHEM and GOME Tropospheric Column Ozone

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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

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GOME Tropospheric Column Ozone RetrievalOzone profile and tropospheric ozone: directly retrieved from GOME Ultraviolet radiance spectra with the LIDORT modelRodgers’ optimal estimation with v8-TOMS climatological a prioriWavelength range: 289-307 nm, 326-340 nmPerform 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 stratosphereSpatial resolution: 960×80 km2 ; Global coverage: 3 days in the equatorRetrieval characterization:

A priori influence: ~15% in the tropics to ~50% at high-latitudesPrecision: ~6% (1.5 DU) in the tropics to ~12% (3 DU) at high-latitudesSmoothing error: ~12% (3 DU) in the tropics to ~25% (6 DU) at high-latitudes

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Tropopause, GEOS-CHEM Sampling and AdjustmentNCEP tropopause: thermal tropopauseECMWF dynamic tropopause: 2.5 pvuGlobal tropopause: minimum between NCEP and dynamic tropopause

GEOS-CHEM: v6.13, 2.5º × 2 ºDifferent spatial and vertical resolutionsGEOS-CHEM Adjustment

Sampling GEOS-CHEM data

Apply GOME retrieval averaging kernels

Integrate to the same tropopause

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GOME vs. GEOS-CHEM

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

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GOME vs. GEOS-CHEM

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GOME vs. GEOS-CHEM

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GOME vs. GEOS-CHEMPoor 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

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Comparison vs. Mozaic/Ozonesonde-Central America

-1.63.20.8-6.02.82.5

Bias

0.850.200.570.420.380.67

R

GOME

BiasR

GEOS-CHEM

MexicoPuerto RCaracasParama.BogotaSan C

6.9-0.211.10.408.70.540.60.338.30.08.80.87

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Comparison vs. Mozaic/Ozonesonde-Southeast Asia

-4.52.8-1.0-2.4-2.82.5

Bias

0.660.620.840.830.880.64

R

GOME

BiasR

GEOS-CHEM

DelhiNahaHanoi

BangkokMadrasKuala L

6.60.747.50.869.60.937.20.947.50.897.30.83

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

-0.2-0.7-1.5-5.1-3.8-3.1Bias

0.950.950.960.73-0.370.16

R

GOME

BiasR

GEOS-CHEM

AnkaraTeheranTela vivDubai+Dakar

Lagos+

0.70.925.40.941.40.945.30.865.20.81-1.10.92

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Comparison vs. Mozaic/Ozonesonde-North Europe

-1.20.89-0.40.34Brussels0.80.941.50.42Frank.0.50.940.20.80Vienna

BiasRBiasR

GEOS-CHEM

GOME

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SummaryThe 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.