Intercomparison of tropospheric ozone profiles obtained by electrochemical sondes, a ground based lidar and an airborne UV-photometer

Eight simultaneous tropospheric ozone profiles have been recorded during an intercomparison campaign at Observatoire de Haute Provence in Southern France from 23 March 1991 to 3 April 1991. The participating instruments were electrochemical sondes of ECC type (Meteo France, CNRM/GMEI), of Brewer-Mast type (Service dʹAeronomie, CNRS), a ground-based UV-DIAL lidar (Service dʹAéronomie, CNRS) and an airborne UV-photometer (Meteo France, CNRM/CAM). Averaged over a 4.5–8 km height range, the biases derived with respect to the median ozone concentration of the four instruments are + 25 ± 3% for ECC sondes, −1 ± 3% for Brewer-Mast sondes, − 3 ± 2% for the airborne UV-photometer and − 7 ± 2% for the lidar. Applying the Dobson normalisation to ECC sondes, its bias is reduced to + 18%, part of which (up to 7%) may be explained by an incorrect estimation of the background current evolution following the standard procedure recommended for ECC sondes (Vaïsala, OES 11 Ozonesonde Userʹs Guide, 1988). The precision derived from the results of this campaign is 10% for ECC sondes, 9% for Brewer-Mast sondes, 5% for the UV-photometer and 5% for the lidar in the troposphere. These results are compared to that of previous intercomparison campaigns and discussed with respect to possible measurement errors related to the different instruments.