Tropospheric ozone is important both as an oxidant and as a greenhouse gas. It may have implications for human health and vegetation. It can be transported from the stratosphere or from the boundary layer into the free troposphere, and then it can be subjected to the long range transport over oceans and continents. The aim of this thesis is to contribute to the analysis of long term trends of the ozone concentrations in the troposphere and to the understanding of the sources of the temporal variability. We used measurements of two instruments based at the Observatoire de Haute Provence (OHP) in the south of France (44˚N, 6.7˚E), the ECC sondes (Electro-chemical Concentration Cell) and the UV DIAL lidar. Our study has shown that this is necessary to combine both data sets to take into account the different meteorology conditions. Our analysis shows a bias of about 1.3 ppb between the seasonal means of ozone measured by each instrument, which is consistent with the results of the inter- comparison campaign, but, which is much weaker than the strong differences (> 7 ppb) due to the variability of the transport because of the difference of sampling. In combining both data sets, the link between the ozone variability and the transport variability (NAO, tropopause height, air masses origin) has been studied. In the upper and the mid-troposphere, no significant trend is observed beside a significant correlation with the NAO index and a change for the last decade of the contribution in ozone of some transport regime at 500 hPa. However, a negative trend after 2000 is observed in the lower troposphere. It can be explained by an increase of the mixing layer height with an increase of the flux coming from the south and the decrease of the contribution in ozone of this transport regime. To characterize the air masses coming to OHP, we used other parameters like the specific humidity, the potential vorticity and the aerosols, which can explain some sources of ozone variability. However, the contribution of the aerosols measurements of the spatial lidar CALIOP during two years is still limited and more aerosols measurements must be taken into account.
