JUNE 2006: Continental outflow of ozone pollution as determined by
O3-CO correlations from the TES satellite instrument

Collocated measurements of tropospheric ozone (O3) and carbon monoxide (CO) from the Tropospheric Emission Spectrometer (TES) aboard the EOS Aura satellite provide information on O3-CO correlations to test our understanding of global anthropogenic influence on O3. We examine the global distribution of TES O3-CO correlations in the middle troposphere (618 hPa) for July 2005 and compare to correlations generated with the GEOS-Chem chemical transport model and with ICARTT aircraft observations over the eastern United States (July 2004). The TES data show significant O3-CO correlations downwind of polluted continents, with dO3/dCO enhancement ratios in the range 0.4-1.0 mol mol-1 and consistent with ICARTT data. The GEOS-Chem model reproduces the O3-CO enhancement ratios observed in continental outflow, but model correlations are stronger and more extensive. We show that the discrepancy can be explained by spectral measurement errors in the TES data. These errors will decrease in future data releases, which should enable TES to provide better information on O3-CO correlations.

The figure shows O3-CO correlations for July 2005 at 618 hPa from (a) TES, (b) GEOS-Chem with TES averaging kernels applied, and (c) GEOS-Chem with both TES averaging kernels and spectral measurement errors applied. The figure shows the correlation coefficients R and the linear regression slopes dO3/dCO determined by the reduced major axis method. The data are computed in 10x10 grid cells, and interpolated in the plot. White regions correspond to |R| < 0.2. A full description is given in Zhang et al. [2006].