SAOZ measurements of total ozone at Aberystwyth

Ozone vertical columns have been measured at Aberystwyth (52.4 degreesN, 4. 1 degreesW) since March 1991 by a SAOZ UV-visible spectrometer. This paper reports on the quality of this dataset. A comparison with Dobson spectropho tometer 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 effect s were most evident from late 1991 to mid-1992. Secondly, a comparison of a nalyses with different reference spectra shows mean differences between ana lyses with a spread of similar to5% with a standard deviation of 1.3%. This is greater than would be expected for the analyses alone because it also c ontains the uncertainty in the amount of ozone present in the reference spe ctra. Finally, measurements show that there has been an increase in the spr ingtime maximum ozone measurements in 1998 and 1999 and in the overall ampl itude of the seasonal variation. (C) 2001 Elsevier Science Ltd. All rights reserved.