SPECTRAL-ANALYSIS AND TREND OF TOTAL OZONE OBSERVATIONS AT VIGNA-DI-VALLE

Time series analyses of measurements of total ozone make possible an in-depth climatological study of this important stratospheric gas. The Italian Air Force's Vigna di Valle Observatory (42-degrees-N, 12-degrees-E, 262 m a.s.l.) provided a time series of monthly averages (January 1958-December 1988) of total ozone. Spectral analysis and running averages were combined to detect medium- (QBOs of estimated (4 divided-by 5) DU amplitudes) and long-term fluctuations (possible correlation to 11-year solar cycle) and to filter them, leaving any overlapping trends unaltered. Total ozone trend estimates produced by the present study were + 0.1% per decade for the 1959-1987 period and a decrease of -0.4% per decade for the more recent 1970-1987 span, over which a pronounced ozone depletion caused mainly by CFCs is assumed.