For trends, sites needed to have at least six complete years between 2011 and 2020. For annual trends, a site could not have a gap in the time series longer tan four months.
Annual trends between 2011 and 2020 for:
- Particulate matter 10 (PM10) concentrations
- Particulate matter 2.5 (PM2.5) concentrations
- Nitrogen dioxide (NO2) concentrations
- Sulphur dioxide (SO2) concentrations
- Carbon monoxide (CO) concentrations
- Ground-level ozone concentrations
Variables:
pollutant: abbreviated pollutant name, chemical name, or chemical formula (e.g., PM10, Ozone, or CO)
site: regional council or unitary authority unique name for site
airshed: gazetted name of airshed
lat: site latitude
long: site longitude
likelihood: trend direction (“improving, “worsening”, or “indeterminate” – for more information see Stats NZ indicator webpages).
significant: TRUE if the trend is statistically significant, otherwise FALSE
p: p-value to assess level of statistical significance
slope: slope of the trend line (average units/year change)
lower: lower limit of the 95% confidence interval of the slope
upper: upper limit of the 95% confidence interval of the slope
intercept: intercept of the trend line
lower_intercept, upper_intercept: trend statistics
slope_percent, lower_percent, upper_percent: trend statistics
trend_type: type of trend (i.e., annual or seasonal)
period_start: first year of the trend period
period_end: last year of the trend period
