Modelling photochemistry in alpine valleys Laboratory of Geophysical and industrial Fluid Flows (University J. Fourier, INP Grenoble, CNRS), BP53, 38 041 Grenoble cedex, France
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. NOy
according to O3 reduction demonstrates a VOC controlled regime,
different from the NOx controlled regime expected and observed in the nearby
city of Grenoble.
Citation: Brulfert, G., Chemel, C., Chaxel, E., and Chollet, J. P.: Modelling photochemistry in alpine valleys, Atmos. Chem. Phys., 5, 2341-2355, doi:10.5194/acp-5-2341-2005, 2005.