Stratospheric ozone measurements made by a ground-based microwave radiometer at the Bordeaux Observatory, France

Measurements of stratospheric ozone are made with a microwave radiometer tuned to the 110.836 GHz ozone line using the beam-switching observing technique proposed by Parrish et al. (1988). The line-of-sight of the instrument is alternately directed towards a low elevation direction and towards the zenith used as reference. The balance between signals obtained in both directions is realized by putting an absorber in the reference direction. The forward model taking into account the observing method produces modelled spectra that agree within 5% with measured ones. The analysis uses the Backus-Gilbert method to retrieve vertical ozone profiles within the altitude range 25 to 75 km with a vertical resolution of 6 km and the sequential optimal estimation proposed by Rodgers is then used to quantify various errors. Retrieved amounts are analyzed in order to estimate the diurnal and seasonal variations of ozone at different altitudes