Modelling photochemistry in alpine valleys

Abstract

Abstract. Road traffic is a serious problem in the Chamonix Valley, France: traffic, noise and above all air pollution worry the inhabitants. The big fire in the Mont-Blanc tunnel made it possible, in the framework of the POVA project (POllution in Alpine Valleys), to undertake measurement campaigns with and without heavy-vehicle traffic through the Chamonix and Maurienne valleys, towards Italy (before and after the tunnel re-opening). Modelling is one of the aspects of POVA and should make it possible to explain the processes leading to episodes of atmospheric pollution, both in summer and in winter. Atmospheric prediction model ARPS 4.5.2 (Advanced Regional Prediction System), developed at the CAPS (Center for Analysis and Prediction of Storms) of the University of Oklahoma, enables to resolve the dynamics above a complex terrain. This model is coupled to the TAPOM 1.5.2 atmospheric chemistry (Transport and Air POllution Model) code developed at the Air and Soil Pollution Laboratory of the Ecole Polytechnique Fédérale de Lausanne. The numerical codes MM5 and CHIMERE are used to compute large scale boundary forcing. This paper focuses on modelling Chamonix valley using 300-m grid cells to calculate the dynamics and the reactive chemistry which makes possible to accurately represent the dynamics in the Chamonix valley (slope and valley winds) and to process chemistry at fine scale. The summer 2003 intensive campaign was used to validate the model and to study chemistry. NO y according to O 3 reduction demonstrates a VOC controlled regime, different from the NO x controlled regime expected and observed in the nearby city of Grenoble.

Seasonal variations of the water soluble organic carbon mass fraction of aerosol in two valleys of the French Alps

“…This hypothesis could be supported by the large impact of imported air-masses demonstrated for the modulation of the ozone concentrations in the valleys in summer (Brulfert, 2004 ;Brulfert et al, 2005a). Furthermore, this hypothesis could explain the same shift of 4 • C that is also seen in Figs.…”

“…The general goal of the POVA program was to compare the air quality and modelled atmospheric emissions and transport in these two valleys before and after the re-opening of the TMB to heavy-duty traffic. The program included several intensive field campaigns, a long-term campaign, and 3-D modelling of atmospheric dynamics and chemistry (Brulfert et al, 2005a).…”

Evolution of the chemical fingerprint of biomass burning organic aerosol during aging

“…Phys. (Table 1) (in a range of 50 to 252 ppb, compared to 40 -50 ppb in areas heavily impacted by biomass burning (Brulfert et al, 2005;Sandradewi et al, 2008)). Experiments conducted at higher NO x concentrations (i.e.…”

Seasonal variation of PM<sub>10</sub> main constituents in two valleys of the French Alps. I: EC/OC fractions

“…The program POVA (Pollution des Vallées Alpines) started in May 2000. The objectives were to develop atmospheric modelling at the sub meso scale (Brulfert et al, 2005), in order to perform scenarios studies of the impact on air quality of changes of traffic and of local developments, taking into account gas and particles emissions. One aspect of the program consisted in a longer-term daily sampling at one site in each valley for a set of properties Published by Copernicus GmbH on behalf of the European Geosciences Union.…”