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

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 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

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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

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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-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

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Comparison vs. Mozaic/Ozonesonde-Central America

GOME GEOS-CHEM

R Bias R Bias

San C 0.67 2.5 0.87 8.8

Bogota 0.38 2.8 0.0 8.3

Parama. 0.42 -6.0 0.33 0.6

Caracas 0.57 0.8 0.54 8.7

Puerto R 0.20 3.2 0.40 11.1

Mexico 0.85 -1.6 -0.2 6.9

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Comparison vs. Mozaic/Ozonesonde-Southeast Asia

GOME GEOS-CHEM

R Bias R Bias

Kuala L 0.64 2.5 0.83 7.3

Madras 0.88 -2.8 0.89 7.5

Bangkok 0.83 -2.4 0.94 7.2

Hanoi 0.84 -1.0 0.93 9.6

Naha 0.62 2.8 0.86 7.5

Delhi 0.66 -4.5 0.74 6.6

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

GOME GEOS-CHEM

R Bias R Bias

Lagos+ 0.16 -3.1 0.92 -1.1

Dakar -0.37 -3.8 0.81 5.2

Dubai+ 0.73 -5.1 0.86 5.3

Tela viv 0.96 -1.5 0.94 1.4

Teheran 0.95 -0.7 0.94 5.4

Ankara 0.95 -0.2 0.92 0.7

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Comparison vs. Mozaic/Ozonesonde-North Europe

GOME GEOS-CHEM

R Bias R Bias

Vienna 0.80 0.2 0.94 0.5

Frank. 0.42 1.5 0.94 0.8

Brussels 0.34 -0.4 0.89 -1.2

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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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