Evaluation of local ozone production of Chamonix valley (France) during a regional smog episode

Proceedings of the 27 NATO/CCMS International Technical Meeting on Air Pollution Modeling and Its Application held in Banff, Canada, 24-29 October 2004.During the summer 2003 a POVA Intensive Observation Period (IOP) aimed at determining the sources of airborne pollutants and monitoring their concentrations in two French Alpine valleys: the Chamonix and the Maurienne valleys (see figure 1 for geographic location). The Pollution of Alpine Valleys (POVA) program was launched in 2000 after the traffic interruption under the Mont-Blanc that followed the tragic accident in the tunnel. The Mont-Blanc tunnel was reopened at the end of 2002 and caused the high duty vehicle traffic (about 1100 trucks per day) to be back in the Chamonix valley. The summer 2003 IOP took place from 5 to 12 July in the Chamonix valley. A high ozone event occurred from 5 to 14 July at regional scales and was well characterised by measurements at rural monitoring sites. To better understand the particular atmospheric circulation, and to study the chemical reactions of airborne pollutants within the valleys, mesoscale modelling is applied. For meteorological calculation, the fifth generation PSU/NCAR Mesoscale Model (MM5) was used at scales ranging from 27 to 1 km. MM5 was coupled with the Chemistry Transport Model (CTM) CHIMERE at regional scales and with the CTM TAPOM at a one-kilometre resolution. Simulations were performed for the period 5-12 July 2003 with different emission sets aiming at studying the impact of the international road traffic in the valley on airborne pollutant concentrations

Atmospheric emission inventory of Maurienne valley for an atmospheric numerical model

Within the framework of an air quality study of the French alpine valleys (POVA program), an atmospheric emission inventory concerning major pollutants: CO, NOx, SO(2), CH(4), particles (PT) and non-methane volatile organic compounds (NMVOC) was carried out. This inventory has a spatial resolution of 1 km(2) and was established for the reference year 2003. The coexistence of economic activities and the Vanoise national park makes the Maurienne valley a sensitive site, particularly representative of the problems of sustainable development in alpine areas, where air pollution is one of the most important aspects. The area, which covers 4588 km(2), is an alpine valley that is sensitive to air pollution due to the emission sources (traffic, industries, private heating, etc.), its morphology (a narrow valley surrounded by high ranges), and local meteorology (temperature inversions and slope winds). As expected, the result which includes both biogenic and anthropogenic sources shows serious emissions of pollutants that are mainly due to the presence of highways and industries around. Two emission inventories were drawn up: one with emission factors determined by CORINAIR (from the European Environment Agency) and the other with emission factors determined by BUWAL-OFEFP (from Swiss Agency for the Environment, Forests and Landscape). The inventories were then compared thanks to concentrations calculated from a numerical model. Computations were run for an intensive field observation period from 25 June to 2 July 2003

Modéles d'atmosphère locale et qualité de l'air en région montagneuse, étude de scénarios

La qualité de l'air dans les régions montagneuses dépend d'une dynamique atmosphérique locale aux vallées qui interagit avec les échelles synoptiques de météorologie. La modélisation associe un calcul tri dimenionnel instationnaire de type simulation des grands échelles à des schémas de réaction chimique. Ces modèles sont évalués par comparaison de leurs résultats avec des mesures collectées sur le terrain et par la bonne reproduction de phénomènes typiques de ces régions tels que les vents de vallée et l'évolution diurne de la hauteur de couche mélangée. Les modèles sont utilisés dans le cadre de scénarios pour évaluer des impacts d'émission sur la qualité de l'air. L'imbrication de domaines de calcul permet de prendre en compte la très large gamme d'échelles de mouvement. On s'appuie sur l'étude de deux sites réels : la vallée de Chamonix encaissée entre de fortes pentes, l'agglomération grenobloise avec des émissions de pollution typique d'une ville importante

Modélisation des circulations atmosphériques pour l'étude de la pollution des vallées alpines

jury composé de: Sylvie Cautenet, Philippe Thunis, Laurence Rouïl, Hubet Gallée et Jean-Pierre CholletLocal weather phenomena observed in alpine valleys frequently lead to the accumulation of emitted anthropogenic airborne species in the low layers of the atmosphere. The development of a numerical model allows reproducing the chemical evolution of air mass during POVA intensive period of observations. In Chamonix and Maurienne valley, computations of photochemical indicators (NOy, O3/NOz, H2O2/HNO3) prove the ozone regime to be control by volatile organic compounds. Moreover simulation highlighted that the major part of this secondary pollutant is regionally produced. The development of an indicator who localised ozone production sites can help to define abatement scenarios. The chemical mechanism RACM allows describing the evolution of many species. It is possible to conclude that in winter road traffic and heating are the main sources of volatile organic compounds.Les phénomènes météorologiques locaux observés dans les vallées alpines conduisent fréquemment à l'accumulation des émissions anthropiques dans les basses couches de l'atmosphère. Le développement d'un modèle numérique a permis de reproduire l'évolution chimique de la masse d'air pendant les périodes d'observations intensives du programme POVA. Dans les vallées de Chamonix et de Maurienne, les simulations réalisées démontrent par l'étude d'indicateurs photochimiques (NOy, O3/NOz, H2O2/HNO3) un régime de production de l'ozone contrôlé par les composés organiques volatils ainsi qu'une prépondérance régionale de ce composé secondaire. Le développement d'un indicateur localisant les zones de production de l'ozone peut aider à définir des scénarios d'abattement. Le mécanisme chimique RACM permet de décrire l'évolution de nombreuses espèces, il est possible de conclure qu'en hiver, le trafic routier et le chauffage sont les principaux émetteurs des composés organiques volatils

Photochemistry in a convective layer and atmosphere dynamics in narrow valley

ISBN 3-901351-59-0 pp. 309-31