SOFRID-O3 v3.5: improvements of tropospheric Ozone retrievals using climatological a priori profiles

For the first time, we have implemented a comprehensive dynamical a priori profile which takes the pixel location, time and tropopause height into account for IASI O₃ retrievals . The use of this dynamical a priori profile largely improves the retrievals concerning two main aspects: (i) it corrects high biases for low-tropospheric O₃ regions such as the Southern Hemisphere, and (ii) it increases the retrieved O₃ variability, leading to a better agreement with ozonesonde data. Concerning upper troposphere–lower stratosphere (UTLS) and stratospheric O₃, the improvements are less important. The SOFRID tropospheric ozone columns display no significant drifts (<2.5 %) for the Northern Hemisphere but significant negative ones (4.3 %) for the Southern Hemisphere (see Barret et al., 2020, https://amt.copernicus.org/articles/13/5237/2020/amt-13-5237-2020.pdf)

Figure: Time serie of differences between SOFRID-O3 v3.5 and sonde data (from the WOUDC network) for surface-300 hPa columns for the Northern Hemisphere (0-90 N). Red lines for raw sonde data and green lines for smoothed sonde data (from Barret et al., AMT, 2020).