Impact of the extreme meteorological conditions during the summer 2003 in Europe on particulate matter concentrations

Abstract Due to the strong relation between meteorology and air quality, a changing climate is anticipated to significantly impact air pollution. To investigate this effect a synoptic situation in the past which is expected to occur more often in future is analyzed in terms of air quality. In this study the effect of the meteorological conditions in the extreme summer 2003 on the concentration of PM10 and its components is investigated over Europe. To this end measurements of the EMEP network in Europe of the summer 2003 were compared to the average of the summers of a five years period (2003–2007). Furthermore simulation runs were performed with the German chemistry transport model REM-Calgrid and the Dutch model LOTOS-EUROS, to analyze whether state-of-the-art chemistry transport models are able to reproduce the observed concentrations during this episode. The synoptic situation in summer 2003 resulted in 1–10 μg m −3 higher observed PM10 concentrations compared to the five years average. This increase was not reproduced to the same extent by the two models at most of the stations and the two models show evident differences in their PM10 simulations. The correlation between PM10 concentrations and meteorological parameters indicates that observed concentrations increase during weather conditions with high daily maximum temperature. The same holds for elemental carbon which is chosen as an example for a primary component. Low horizontal transport and the absence of wet deposition as a result of low wind speed and little precipitation associated with conditions with high temperatures favour the accumulation of pollutants in the lower troposphere. Although these conditions are reflected in the meteorological input data of the chemistry transport models used in this study, the models were not able to reproduce this relationship; they underestimate the observed high concentrations. This indicates that the underestimation of the variability of PM with meteorology is due to missing but important components and associated emissions or uncertainties therein, e.g. mineral dust, secondary organic aerosols and wild fires. To improve the simulation performance of the chemistry transport models as function of meteorological conditions these emission sources and the formation of secondary organic aerosols have to be included or improved and the dependency of anthropogenic emissions on meteorological conditions should be explicitly taken into account. These are essential issues for the simulation of such extreme conditions.