Measurements of total and tropospheric ozone from IASI: comparison with correlative satellite and ozonesonde observations

In this paper, we present measurements of total and tropospheric ozone, retrieved from infrared radiance spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI), which was launched on board the MetOp-A European satellite in October 2006. We compare the IASI total ozone columns to observations from the Global Ozone Monitoring Experiment-2 (GOME-2) for one full year of observations (2008). The global distributions are in good agreement, with a correlation coefficient better than 0.9. On average, IASI ozone retrievals exhibit a positive bias compared to GOME-2 of about 4.9 DU (2.9%) to 13 DU (4.4%) depending on the season. In addition to total ozone columns, the good spectral resolution of IASI enables the retrieval of tropospheric ozone concentrations. Comparisons of IASI tropospheric columns to 490 collocated ozone soundings available from several stations around the globe have been performed for the period June 2007–August 2008. IASI tropospheric ozone columns compare well with sonde observations, with correlation coefficients of 0.95 and 0.77 for the [surface – 6 km] and [surface – 12 km] partial columns, respectively. IASI retrievals tend to overestimate the tropospheric ozone columns in comparison with ozonesonde measurements. Positive average biases of 0.15 DU (1.2%) and 3 DU (11%) are found for the [surface – 6 km] and for the [surface – 12 km] partial columns, respectively.