SAOZ measurements of total ozone at Aberystwyth

Abstract

Ozone vertical columns have been measured at Aberystwyth (52.4°N, 4.1°W) since March 1991 by a SAOZ UV-visible spectrometer. This paper reports on the quality of this dataset. A comparison with Dobson spectrophotometer measurements from Camborne shows clearly how SAOZ measurements were strongly affected by aerosol from the Mt. Pinatubo volcanic eruption: air mass factors were reduced by aerosol layers in the stratosphere. The effects were most evident from late 1991 to mid-1992. Secondly, a comparison of analyses with different reference spectra shows mean differences between analyses with a spread of ∼5% with a standard deviation of 1.3%. This is greater than would be expected for the analyses alone because it also contains the uncertainty in the amount of ozone present in the reference spectra. Finally, measurements show that there has been an increase in the springtime maximum ozone measurements in 1998 and 1999 and in the overall amplitude of the seasonal variation.