Abstract : B.2
Influence of meteorological processes on wintertime pollution episodes during the Brenner-South ALPNAP measuring campaign

Massimiliano De Franceschi, Dino Zardi
University of Trento - Dept. of Civil and Environmental Eng.

Results of an intensive field campaign performed within the project ALPNAP (funded by the European Regional Development Fund (ERDF) - Interreg III B initiative) between January and mid March 2006 along the River Adige Valley (Northern Italy) are presented. Three specific target areas have been identified aiming at highlighting to what extent the local meteorology is influenced by the topography and how the complex and varying meteorological phenomena affect the transport of air pollutants, primarily those emitted by the motorway running along the whole valley.

The experimental setup included 4 air quality mobile stations across the valley bottom and the slopes in order to get information on the spatial distribution of the different pollutants; a complete energy-balance measurement system on the valley bottom, along with a sodar for the determination of the wind profile up to a height of approximately 400 m agl.; a set of 5 air temperature and RH sensors along the slopes for a pseudo-vertical temperature profile.

The good performance of the whole setup allowed a more detailed picture of the complex processes leading to the high-concentration episodes typical of the winter season. Some of the specific and interesting features highlighted by the field measurements can be summarized as follows:

1. similar meteorological and emission “boundary” conditions lead to different effects due to local-scale phenomena; 2. strong thermal stratifications as a major responsible for stagnation and limited dilution along with a complex vertical wind structure; 3. influence of shallow Foehn events in increasing the concentration levels close to the ground; 4. presence of weak up- and down-valley winds whose outflow towards the Po plain is often blocked, thus inducing a constant enrichment in pollutants of the lowest atmospheric layers.

All these information also allowed a more reliable modelling of both the meteorological fields and the pollutant transport (Antonacci et al.).