Long-Range Transport of Pollutants Above the Eastern Mediterranean: Implications for Air Quality and Regional Climate

The present work provides an overview of the transport and transformation processes occurred above the Mediterranean with emphasis in the Eastern basin. It summarises the results from several campaigns performed since the last decade. The measurements gave evidence of a remarkably high level of air pollution from the surface to the top of the troposphere up to 15 km altitude. The strongest anthropogenic influence was observed in the lower 4 km by pollutants originating from both Westand East Europe transported by the northerly flow. The sources are industrial activity, traffic, forest fires, agricultural and domestic burning. Trajectory analysis and model results suggest also an important influence by Asian pollution plum near the tropopause from the east.

Near the surface the air pollution has several undesirable consequences. First, the European Union eight-hourly air quality standard for ozone is exceeded throughout the summer in the entire Mediterranean region. Second, the concentrations of aerosols are high as well, affecting human health. The aerosols furthermore influence the Mediterranean atmospheric energy budget by scattering and absorbing solar radiation. During summer, they reduce solar radiation absorption by the sea by about 10% and they alter the heating profile of the lower troposphere. As a consequence, evaporation and moisture transport, in particular to North Africa and the Middle East, are suppressed.

In the free troposphere, pollution is largely determined by intercontinental transport, whereas upper tropospheric pollution from Asia can reach the stratosphere. These “crossroads” carry large pollution loads over the Mediterranean, and the negative effects extend far beyond the region. International efforts are called for to reduce these atmospheric environmental stresses and to further investigate the links between Mediterranean and global climate change.