Lidar measurements and Umkehr observations of the ozone vertical distribution at the Observatoire de Haute-Provence

Abstract

Lidar measurements and Umkehr observations of the ozone vertical distribution are performed routinely at the Observatoire de Haute-Provence (44 N, 5 E), since respectively 1985 and 1983. as part of the newly implemented Automated Dobson Network and Network for the Detection of Stratospheric Changes. From 1985 to 1988, the corresponding data base includes more than 1000 Umkehr observations and 95 lidar profiles, allowing for a comparison between the two methods over 82 coincidences. Such a comparison has been performed with respect to the three Umkehr retrieval methods presently available : conventional Umkehr, short Umkehr and the newly developed ‘new-conventional’ Umkehr methods. The analysis shows that the ozone values, as retrieved by the new-conventional Umkehr method, which takes into account more accurately the natural variability of the ozone vertical distribution and the temperature influence on the ozone absorption coefficients, are in rather good agreement with the lidar measurements. No statistically significant bias can be observed in the Umkehr layers 4 to 7 between the two methods of measurement. In the Umkehr layer 8, a positive bias between the Umkehr retrievals and the lidar measurements can be observed, mainly during the winter months, which can be accounted for by signal induced noise effects leading to an underestimate of the ozone concentration from the lidar measurements, and by the large variability in the daily temperature profiles as observed during the same period of the year.