Long-Term Multi-Mission Validation of Ozone and Temperature Profiles by the Validation with Lidar (VALID) Project

International audience; The Satellite validation with lidar (VALID) project supports the long-term multi-mission validation of atmospheric chemistry and physics instruments with ground-based lidars. VALID involves lidar stations around the world measuring stratospheric ozone and temperature profiles, and tropospheric aerosol and cloud properties. Currently around ten thousand lidar profiles have been made available for validation purposes in VALID and its predecessor EQUAL (ENVISAT quality assessment with lidar). The satellite data under investigation here are the ozone and temperature profiles delivered by the MIPAS (Michelson interferometer for passive atmospheric sounding) and SCIAMACHY (Scanning imaging absorption spectrometer for atmospheric chartography) instruments as new algorithms have become available recently. We have collocated the satellite profiles with the lidar measurements and analysed the comparison results for dependence on several geophysical and instrument observational parameters. Results for the delta validation are presented for SCIAMACHY level 2 version 5.01 and for MIPAS level 2 version ORM (optimised retrieval model) 5.0x. For the SCIAMACHY validation, additional ozone sonde and microwave radiometer data have been included to enlarge the validation dataset. The consistent underestimation of the ozone concentrations by SCIAMACHY seen in version 3.01 is now removed. In the mid-latitudes, SCIAMACHY version 5.01 matches the validation instruments within 5% up to 38 km altitude. The cloud free data are more positively biased. In the polar regions, there is a variable bias ranging from -10% to +7% in the altitude range 15 to 35 km, increasing above (its magnitude depending on validation instrument). The cloud free data have a more enhanced negative bias. In the tropics, there is positive bias in SCIAMACHY v5.01 (5 to 23%) and the cloud free data appear to have a more positive bias (few percent). The large deviation at low altitudes could be due to sub-visual cirrus and will be further investigated in the future. Finally, with respect to the observation direction (corresponding to the scan angle), Eastern orientated profiles overall have a more negative bias than Western profiles For the MIPAS version 5.0x data, the ozone profiles match the lidar data very well over a large part of the compared altitudes. Deviations are seen at the bottom of the profiles starting with a positive bias when going down below the ozone maxima reaching up to +5%. In the tropics this bias changes sign when reaching the lower most altitudes and gets to -10%. At the highest altitudes there is a positive bias in the tropics (max. 2%) and in the mid-latitudes (max. 5%), whereas in the polar region there is an increasing underestimation from an altitude of 35 km (close to 0%) towards the top at 45 km (nearly 15%). The temperature data are mostly within 1 to 2 K from the lidar data. Looking at the different altitude axis, we cannot say that using the engineering altitudes gives a better performance than when using the corrected altitude axis. In fact, the comparison improves when introducing a shift of +500 m for the MIPAS data in the polar region and mid-latitudes (larger shift needed for the tropics). This is not seen in the ozone data and thus needs further study.