Keywords: air pollution, mesoscale modelling, complex terrain, Alpine Valleys, photochemistry, ozone production, atmospheric dispersion modelling, France, air quality, pollutant concentration
Production of ozone in the Chamonix Valley (France)
In the framework of the Pollution of Alpine Valleys (POVA) programme, a numerical investigation aims to better understand how a reduction of traffic emissions can affect air quality in the Chamonix Valley (France). The MM5 model coupled with the Chemistry Transport Model (CTM) TAPOM using a 1-km cell grid for the period 5–12 July 2003 showed that the ozone formation in the Chamonix Valley was strongly NOx-saturated. A comparison with physical and chemical measurements (tethered balloon, UHF radar, monitoring data) prove the temperature profile and the up- and downhill thermally driven winds to be reasonably well described by MM5. Moreover spatial and temporal variation of O3 concentration is well described by TAPOM. Ozone production within the valley is estimated to 20 to 30 µg/m³ and 10 µg/m³ are locally produced from precursors emitted by international traffic through the tunnel.