Meteorological variability in NO2 and PM10 concentrations in the Netherlands and its relation with EU limit values

Abstract The extent of the exceedance of the EU limit values for nitrogen dioxide (NO 2 ) and particulate matter (PM 10 ) concentrations within the Netherlands is expected to decrease significantly, in the coming years. Whether limit values will actually be exceeded, in the next decade, depends not only on European, national and local policies, but also on the effects of inevitable interannual meteorological fluctuations. An analysis of model calculations and measurements yields variations (1 sigma) in the annual average concentration of about 5% for NO 2 and 9% for PM 10 , due to meteorological fluctuations. These deviations from long-term average concentrations affect assessments of future levels, set against limit values. For instance, an NO 2 concentration of 39 μg m −3 , estimated for a given year with long-term average meteorology, indicates that it is likely (chance >66%) that the limit value of 40 μg m −3 will not be exceeded in that particular year. At the same time, the estimation also indicates, for example, that this situation is unlikely (change −3 , it is likely that the limit value will not be exceeded for three years in a row. The limit value for the daily average PM 10 concentration is equivalent to an annual average of about 32 μg m −3 . This threshold is unlikely to be exceeded for three years in a row, when an annual average concentration of 29 μg m −3 is estimated. Interannual variations in concentrations of NO 2 and PM 10 are linked to large-scale meteorological fluctuations. Therefore, similar results can be expected for other European countries.