Onset of the total ozone increase based on statistical analyses of global ground-based data for the period 1964-2008

The zonally averaged total column ozone from ground-based observations for the period 19642008 is being examined to detect changes in the trend pattern. The ozone long-term changes for the periods 19801995 and 19962008 are estimated through the use of a triad of regression models that differ in the description of a trend term. The trend term could be proportional to the amount of ozone-depleting substances in the atmosphere, or has a piecewise linear form with turning points in 1980 and 1996, or described by any smooth curve. The standard indices of the ozone dynamical drivers: 10.7 cm solar flux, zonal component of the stratospheric wind in the tropics, the Arctic, and Antarctic Oscillation index, and the vertical component of the Eliassen-Palm flux are used to parameterise the ozone response to changes in the atmospheric dynamics. The trends are calculated separately for each season and for the entire year by using the aggregated monthly mean data over broad latitudinal zones: SH polar (90 S-65 S), SH midlatitudes (60 degrees S-30 S), Tropics (25 degrees S-25 N), NH midlatitudes (30 N-60 N), NH polar (65 degrees N-90 N), 50 degrees S-50 N band, and the entire globe (90 degrees S-90 N). All versions of the trend model give statistically significant (at the 95% confidence level) positive trends of similar to 0.5-1.0% per decade for the period 1996-2008 over the whole globe (boreal spring), and over 50 degrees S-50 N zone (boreal summer and the entire year). An agreement between trend values by various trend models with different parameterisation of the dynamically driven ozone variations builds a strong support for changes in the trend pattern since the mid-1990s. Copyright (C) 2010 Royal Meteorological Society