HR: 1340h
AN: A43C-0070    [Abstracts]
TI: Regional scale impacts on an elevated high ozone episode in the Alps
AU: * Couach, o
EM: olivier.couach@epfl.ch
AF: EPFL-ENAC-LPAS, Chemistry building, Lausanne, 1015 Switzerland
AU: Ristori, P
EM: pablo.ristori@epfl.ch
AF: EPFL-ENAC-LPAS, Chemistry building, Lausanne, 1015 Switzerland
AU: Chaxel, E
EM: Eric.Chaxel@hmg.inpg.fr
AF: LEGI-THEO, INPG-UJF, Grenoble, 38041 France
AU: Kirchner, F
AF: EPFL-ENAC-LPAS, Chemistry building, Lausanne, 1015 Switzerland
AU: Van den Bergh, H
EM: veronique.bauler@epfl.ch
AF: EPFL-ENAC-LPAS, Chemistry building, Lausanne, 1015 Switzerland
AB: Ozone events in urban regions are a major atmospheric pollution problem in Europe. During the summer of 1999, a field campaign GRENOble PHOTochemistry (GRENOPHOT) was held in the Grenoble metropolitan region, in the French Alps, in order to obtain high resolution (spatial and temporal) measurements for air quality modeling assessment. The meteorological and atmospheric chemistry simulations were validated using both near ground and atmospheric profile measurements (e.g. lidar measurements of ozone) during the Intensive Observation Period (IOP): observations 25$^{th}$-27$^{th}$ July. Of particular interest were a series of lidar which showed between 2000 and 2500 meters elevated ozone levels during the night of 26$^{th}$ and 27$^{th}$. In order to understand the origin of these high ozone levels we apply a series of mesoscale models focusing from Europe to the Rh\^{o}ne-Alpes region and down to the urban scale to distinguish local ozone production from ozone transported. At the European scale MM5 was used to simulate the meteorological fields coupled with the Chemistry Transport Model CHIMERE with a 27-kilometer mesh resolution covering Central Europe. At the regional and local scales, the air quality model METeorological PHOtochemistry MODel (METPHOMOD) was used with a 6 km mesh resolution for the regional grid and at a 2 km resolution mesh for the smaller urban grid. This chain of mesoscale models is applied with a nesting procedure which couples the individual model simulations. Ozone mixing ratios, run at the large scale, demonstrated the advection of ozone at higher altitudes during the night and the last day of the IOP from the Mediterranean sea. Moreover, the contribution of NOx and VOC clearly showed an important contribution to the near surface ozone mixing ratio. This chain of nested models improves the prediction of the vertical ozone distribution and explains the source of the ozone measured by lidar in the free troposphere.
DE: 0345 Pollution--urban and regional (0305)
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting