[1] During the Atmospheric Pollution Over the Paris Area (ESQUIF) experiment a series of airborne measurements were collected in the vicinity of the city of Paris during smog episodes. They are used in combination with an air quality photochemical model in order to diagnose uncertainties in the current emission inventory. Diagnostics are made by comparing simulated with observed concentrations for nitrogen oxides, carbon monoxide, and primary hydrocarbons, taking into account the chemistry and transport processes of these compounds. An emphasis is put on the uncertainty of the results, taking into account the finiteness of the measurement samples, possible errors in the model transport, and chemistry and measurement errors. We examine, in particular, possible sources of bias in the model. For instance, we show that boundary layer depth is underestimated by at most 30% on average. However, sensitivity experiments showed that these model biases, taken individually, cannot alter the qualitative aspects of our results. Only a conspiracy of these biases could possibly shift all our diagnostics toward significantly different results. There is reasonable consistency between simulated and measured concentrations. NO y simulations agree with measured concentrations to within 35%; CO concentrations agree to within a factor of 2. There are significant underestimations and overestimations in some individual primary hydrocarbons. However, the total mass and reactivity of the measured hydrocarbon mixture, which accounts for only about half of the total emitted mass, agree with modeled values to within an estimated uncertainty of 40%. The analysis of results provides clues for improving emission inventories. It is found, for instance, that temperature dependence, which is not considered here, can be a key factor and that hydrocarbon emissions from solvent use may suffer from inaccurate totals or speciation. Another source of uncertainties may be the temporal or spatial distributions of solvent activities.

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In the French Mediterranean basin the large city of Marseille and its industrialized suburbs (oil plants in the Fos-Berre area) are major pollutant sources that cause frequent and hazardous pollution episodes, especially in summer when intense solar heating enhances the photochemical activity and when the sea breeze circulation redistributes pollutants farther north in the countryside. This paper summarizes the findings of 5 years of research on the sea breeze in southern France and related mesoscale transport and dilution of pollutants within the Field Experiment to Constraint Models of Atmospheric Pollution and Emissions Transport (ESCOMPTE) program held in June and July 2001. This paper provides an overview of the experimental and numerical challenges identified before the ESCOMPTE field experiment and summarizes the key findings made in observation, simulation, and theory. We specifically address the role of large-scale atmospheric circulation to local ozone vertical distribution and the mesoscale processes driving horizontal advection of pollutants and vertical transport and mixing via entrainment at the top of the sea breeze or at the front and venting along the sloped terrain. The crucial importance of the interactions between processes of various spatial and temporal scales is thus highlighted. The advances in numerical modeling and forecasting of sea breeze events and ozone pollution episodes in southern France are also underlined. Finally, we conclude and point out some open research questions needing further investigation

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Abstract. The general purpose of this paper is to experimentally study mesoscale dynamical aspects of the Mistral in the coastal area located at the exit of the Rhône-valley Thanks to the use of the time evolution of the vertical profile of the horizontal wind vector, recent works have shown that the dynamics of the Mistral is highly dependent on the season because of the occurrence of specific synoptic patterns. In addition, during summer, thermal forcing leads to a combination of sea breeze with Mistral and weaker Mistral due to the enhanced friction while, during autumn, absence of convective turbulence leads to substantial acceleration as low-level jets are generated in the stably stratified planetary boundary layer. At the exit of the Rhône valley, the gap flow dynamics dominates, whereas at the lee of the Alps, the dynamics is driven by the relative contribution of "flow around" and "flow over" mechanisms, upstream of the Alps. This paper analyses vertical velocity and turbulence, i.e. turbulent dissipation rate, with data obtained by the same UHF wind profilers during the same Mistral events.In autumn, the motions are found to be globally and significantly subsident, which is coherent for a dry, cold and stable flow approaching the sea, and the turbulence is found to be of pure dynamical origin (wind shears and mountain/lee wave breaking), which is coherent with non-convective situations.In summer, due to the ground heating and to the interactions with thermal circulation, the vertical motions are less pronounced and no longer have systematic subsident chara-teristics. In addition, those vertical motions are found to be much less developed during the nighttimes because of the stabilization of the nocturnal planetary boundary layer due to a ground cooling. The enhanced turbulent dissipation-rate values found at lower levels during the afternoons of weak Mistral cases are consistent with the installation of the summer convective boundary layer and show that, as expected in weaker Mistral events, the convection is the preponderant factor for the turbulence generation. On the other hand, for stronger cases, such a convective boundary layer installation is perturbed by the Mistral.

Abstract. This paper investigates experimentally and numerically the time evolution of the spatial distribution of aerosols over the Western Mediterranean basin during 24 March 1998 Mistral event documented during the FETCH experiment. Mistral and Tramontane are very frequent northerly winds (5–15 days per month) accelerated along the Rhône and Aude valley (France) that can transport natural and anthropogenic aerosols offshore as far as a few hundreds of kilometers which can in turn have an impact on the radiation budget over the Mediterranean Sea and on precipitation. The spatial distribution of aerosols was documented by means of the airborne lidar LEANDRE-2 and spaceborne radiometer SeaWIFS, and a validated mesoscale chemical simulation using the chemistry-transport model CHIMERE with an aerosol module, forced by the non-hydrostatic model MM5. This study shows that: (1) the Mistral contributes to the offshore exportation of a large amount of aerosols originally emitted over continental Europe (in particular ammonium nitrate in the particulate phase and sulfates) and along the shore from the industrialized and urban areas of Fos-Berre/Marseille. The Genoa surface low contributes to advect the aerosols along a cyclonic trajectory that skirts the North African coast and reaches Italy; (2) the aerosol concentration pattern is very unsteady as a result of the time evolution of the two winds (or Genoa cyclone position): The Tramontane wind prevails in the morning hours of 24 March, leaving room for the Mistral wind and an unusually strong Ligurian outflow in the afternoon. The wakes trailing downstream the Massif Central and the Alps prevent any horizontal diffusion of the aerosols and can, at times, contribute to aerosol stagnation.

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