TES ozone profiles compared to ozonesondes

The Tropospheric Emission Spectrometer (TES) on the EOS-Aura spacecraft, launched July 15, 2004, is making direct, global observations of tropospheric ozone. Routine observations began in late August 2004. Ozone profiles are retrieved from TES infrared radiances with vertical resolution of roughly 6 km for nadir observations. The principal source of validation for TES O3 measurements is ozonesondes. For this analysis, we focused on data from fall, 2004. In some cases, we have ozonesonde data from dedicated launches timed to match the Aura overpass, while other comparisons are performed with standard data available from the SHADOZ and WOUDC data archives. In order to make TES-ozonesonde comparisons, we must account for TES measurement sensitivity and the disparities in vertical resolution. This is done by applying the TES averaging kernel and constraint to the ozonesonde profile. Differences between TES profiles and the resulting (smoothed) sonde profiles are then compared to expected differences due to estimated retrieval errors, climatological variability and spatial/temporal discrepancies. TES ozone profiles are systematically higher than sondes in the upper troposphere, but compare well in the lower troposphere. TES measurements are able to differentiate tropospheric ozone profiles over a range of (coarse) vertical structures.