Effects of meteorological conditions on concentrations of nitrogen oxides in Auckland

Air quality in Auckland is generally within the na tional guidelines. But at t imes, especially in winter, t he city suffers from air pollution pheno mena such a s a b rown haze, which is thought associated with h igh levels of nitrogen oxides. The e ffects of meteorological conditions on local air quality are quan titatively assessed on a da ily 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 enhan ced d ispersion. 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 e ffects of meteorological conditions are consistent for NO levels, but are significantly different for NO2 levels, suggesting other factors may be important.