New Zealand's Environment Reporting Series: The Ministry for the Environment and Statistics New Zealand
NIWA supplied ozone data in two forms, with different starting dates: - measurements made using a Dobson spectrophotometer (number 72), from 1987 - data assimilated from satellite measurements recalibrated against the global Dobson network, from 1978. NIWA takes measurements using the Dobson spectrophotometer 72 under clear-sky, direct sunlight conditions at Lauder in Otago. There are gaps in the time series due to days with cloud, rain, or too much wind. However, over the whole period, each individual calendar day of the year was measured. This allows us to calculate statistics based on the day of the year. The trend was assessed using the Theil-Sen estimator and the Two One-Sided Test (TOST) for equivalence at the 95% confidence level. More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.