Dynamic evaluation of a multi-year model simulation of particulate matter concentrations over Europe
A 9 yr air quality simulation is conducted from 2000 to 2008 over Europe using the Polyphemus/Polair3D chemical-transport model (CTM) and then evaluated against the measurements of the European Monitoring and Evaluation Programme (EMEP).
The spatial distribution of PM 2.5 over Europe shows high concentrations over northern Italy (36 μg m −3) and some areas of Eastern Europe, France, and Benelux, and low concentrations over Scandinavia, Spain, and the easternmost part of Europe. PM 2.5 composition differs among regions.
The operational evaluation shows satisfactory model performance for ozone (O 3). PM 2.5, PM 10, and sulfate (SO 4=) meet the performance goal of Boylan and Russell (2006). Nitrate (NO 3−) and ammonium (NH 4+) are overestimated, although NH 4+ meets the performance criterion. The correlation coefficients between simulated and observed data are 63% for O 3, 57% for PM 10, 59% for PM 2.5, 57% for SO 4=, 42% for NO 3−, and 58% for NH 4+. The comparison with other recent 1 yr model simulations shows that all models overestimate nitrate. The performance of PM 2.5, sulfate, and ammonium is comparable to that of the other models.
The dynamic evaluation shows that the response of PM 2.5 to changes in meteorology differs depending on location and the meteorological variable considered. Wind speed and precipitation show a strong negative day-to-day correlation with PM 2.5 and its components (except for sea salt, which shows a positive correlation), which tends towards 0 as the day lag increases. On the other hand, the correlation coefficient is near constant for temperature, for any day lag and PM 2.5 species, but it may be positive or negative depending on the species and, for sulfate, depending on the location. The effects of precipitation and wind speed on PM 2.5 and its components are better reproduced by the model than the effects of temperature. This is mainly due to the fact that temperature has different effects on the PM 2.5 components, unlike precipitation and wind speed, which impact most of the PM 2.5 components in the same way.
These results suggest that state-of-the-science air quality models reproduce satisfactorily the effect of meteorology on PM 2.5 and therefore are suitable to investigate the effects of climate change on particulate air quality, although uncertainties remain concerning semivolatile PM 2.5 components.