资源环境科技发展态势分析平台

Ozone (O-3) trends and variability from a 28-year (1987-2014) ozonesonde record at Lauder, New Zealand, have been analysed and interpreted using a statistical model and a global chemistry-climate model (CCM). Lauder is a clean rural measurement site often representative of the Southern Hemisphere (SH) mid-latitude background atmosphere. O-3 trends over this period at this location are characterised by a significant positive trend below 6 km, a significant negative trend in the tropopause region and the lower stratosphere between 9 and 15 km, and no significant trend in the free troposphere (6-9 km) and the stratosphere above 15 km. We find that significant positive trends in lower tropospheric ozone are correlated with increasing temperature and decreasing relative humidity at the surface over this period, whereas significant negative trends in the upper troposphere and the lower stratosphere appear to be strongly linked to an upward trend of the tropopause height. Relative humidity and the tropopause height also dominate O-3 variability at Lauder in the lower troposphere and the tropopause region, respectively. We perform an attribution of these trends to anthropogenic forcings including O-3 precursors, greenhouse gases (GHGs), and O-3-depleting substances (ODSs), using CCM simulations. Results indicate that changes in anthropogenic O-3 precursors contribute significantly to stratospheric O-3 reduction, changes in ODSs contribute significantly to tropospheric O-3 reduction, and increased GHGs contribute significantly to stratospheric O-3 increases at Lauder. Methane (CH4) likely contributes positively to O-3 trends in both the troposphere and the stratosphere, but the contribution is not significant at the 95% confidence level over this period. An extended analysis of CCM results covering 1960-2010 (i.e. starting well before the observations) reveals significant contributions from all forcings to O-3 trends at Lauder - i.e. increases in GHGs and the increase in CH4 alone all contribute significantly to O-3 increases, net increases in ODSs lead to O-3 reduction, and increases in non-methane O-3 precursors cause O-3 increases in the troposphere and reductions in the stratosphere. This study suggests that a long-term ozonesonde record obtained at a SH mid-latitude background site (corroborated by a surface O-3 record at a nearby SH mid-latitude site, Baring Head, which also shows a significant positive trend) is a useful indicator for detecting atmospheric composition and climate change associated with human activities.