[en] The work presented here intends to characterize the variations of atmospheric concentrations of CO₂, CO, O₃ and ultrafine particles, over a large scale aircraft transect above Siberia, during three intensive YAK-AEROSIB campaigns in April 2006, September 2006 and August 2007, respectively. Pollutant and greenhouse gases distribution in this poorly studied region is needed to model atmospheric long range transport. I show here that CO concentrations at the time of the campaigns is broadly affected by (1) advection of Chinese pollutants through baro-clinic perturbations, (2) advection (diffuse or not) of European pollutants at various altitudes, (3) and of biomass burning from Central Asia. This set of factors is analyzed through a novel statistical technique based on clustering of backward transport simulated by the FLEXPART Lagrangian model. Large observed CO₂ gradients in summer are matched against vertical mixing in GCM simulated CO₂. At last I present ultrafine particle measurements, and a possible nucleation summer maximum in the clean, continental mid-troposphere. (author)