Towards improved evaluations of total ozone at the Jungfraujoch, using vertical profile estimations based on auxiliary data

The currently available database of total ozone amounts observed at the Jungfraujoch site in the Swiss Alps starts in 1984, based on high-resolution infrared solar absorption spectroscopic measurements, and has been complemented by daily SAOZ data since mid-1990. The latter instrument (Système d'Analyse par Observations Zénithales) measures the ozone column by application of the DOAS (Differential Optical Absorption Spectroscopy) method to zenith-sky scattered-light spectra in the ultraviolet-visible range, taken at twilight. The actual intercomparison for the overlapping period reveals a negative systematic offset of the FTIR with respect to the SAOZ data of 3.8 % on average, but showing a seasonal variation in the difference. Part of the observed difference probably originates in the model atmospheres that influence the retrieved column differently for each technique. This work shows the development of a climatological ozone vertical distribution model that is more representative of the real atmosphere, exploiting daily meteorological data that are commonly available at the Jungfraujoch site. It argues that the use of this climatological model may improve the accuracy of the retrieved total columns, and hence the agreement between the SAOZ and FTIR datasets; some possible improvements to the model are suggested. Application of this concept to a re-analysis of past observations, making use of existing meteorological long-term records, will enhance the validity of the ozone database at the Jungfraujoch.