Effects of meteorological conditions on concentrations of nitrogen oxides in Auckland

Air quality in Auckland is generally within the national guidelines. But at times, especially in winter, the city suffers from air pollution phenomena such as a brown haze, which is thought associated with high levels of nitrogen oxides. The effects of meteorological conditions on local air quality are quantitatively assessed on a daily basis by determining the relationship between concentrations of nitrogen oxides (NO and NO₂) and several meteorological variables for winter months, from 1990 to 1996. Strong southwesterly winds, the prevalent flow pattern over the region, are associated with good air quality due to enhanced dispersion. Calm, cold conditions lead to the build-up of pollution. Meteorological conditions can explain more variances in NO levels (up to 65%) than in NO₂ levels (up to 26%). For different emission source conditions, the effects of meteorological conditions are consistent for NO levels, but are significantly different for NO₂ levels, suggesting other factors may be important.