Trends and variability in vertical ozone and temperature profiles measured by ozonesondes at Lauder, New Zealand: 1986-1996

A first analysis of trends in vertical ozone and temperature profiles from ozonesonde flights made at Lauder (45.045 degrees S, 169.684 degrees E) between August 1986 and July 1996, is presented. To calculate the trends and determine the magnitude of the forcing mechanisms underlying the variability in ozone and temperature, a linear least squares regression model was applied to ozone mixing ratios, ozone number densities, and temperatures, interpolated onto 100 pressure levels from the surface (969 hPa/370 m) to 12.1 hPa (similar to 30.1 km), similar to 300 geopotential meters apart. Ozone trends indicate wintertime upper tropospheric decreases of more than -30+/-24% per decade (2 sigma), post vortex breakup trends in a-narrow altitude region above the tropopause of -20+/-20% per decade (2 sigma), and positive trends of up to 30+/-14% per decade (2 sigma) in the lower stratosphere during late winter, spring, and early summer. The predominant temperature trend is +1.5% per decade and greater above the similar to 50 hPa level during winter. Derived trends were sensitive to inclusion of tropopause height forcing which was found to influence ozone and temperature at a high level of statistical significance. Ozone at Lauder shows significant QBO dependence throughout the lower stratosphere during winter, spring, and early summer, but little or no dependence on the solar;cycle. Temperatures, however, show little dependence on QBO but were influenced by the solar cycle. The Mt. Pinatubo eruption had little influence on Lauder ozone but significantly cooled the troposphere. The ENSO cycle in ozone and temperature was weak except at the uppermost analysis levels.