Primequal-Predit Escompte, R2 project - Dynamic processes, Final report

The study was dedicated to the analysis of atmospheric dynamics in the area of Fos- Berre-Marseille, to point out the mechanisms of transport, accumulation or dilution of the plumes during photochemical pollution episodes. A large range of spatial scales was investigated. The first point to emphasize is the complexity of boundary layers at small scale, due to the cumulative effect of local winds such as sea-breeze or Mistral and slope breezes and the necessity to use simulations at high resolution. Similarly to during other campaigns (such as ESQUIF), plumes are found more polluted over distant areas (such as mountains) than near the emission areas. Mountains are also likely to be preferred areas for vertical exchanges with the free troposphere that carries pollution from remote areas (either from Spain or from the upper troposphere layers). Ozone budgets revealed to be difficult to obtain experimentally, in spite of the high density of measurements that were performed