The YAK-AEROSIB transcontinental aircraft campaigns: new insights on the transport of CO 2 , CO and O 3 across Siberia

International audienceTwo airborne campaigns were carried out to measure the tropospheric concentrations and variability of CO 2 , CO and O 3 over Siberia. In order to quantify the influence of remote and regional natural and anthropogenic sources, we analysed a total of 52 vertical profiles of these species collected in April and September 2006, every ∼200 km and up to 7 km altitude. CO 2 and CO concentrations were high in April 2006 (respectively 385-390 ppm CO 2 and 160-200 ppb CO) compared to background values. CO concentrations up to 220 ppb were recorded above 3.5 km over eastern Siberia, with enhancements in 500-1000 m thick layers. The presence of CO enriched air masses resulted from a quick frontal uplift of a polluted air mass exposed to northern China anthropogenic emissions and to fire emissions in northern Mongolia. A dominant Asian origin for CO above 4 km (71.0%) contrasted with a dominant European origin below this altitude (70.9%) was deduced both from a transport model analysis, and from the contrasted CO/ CO 2 ratio vertical distribution. In September 2006, a significant O 3 depletion (∼-30 ppb) was repeatedly observed in the boundary layer, as diagnosed from virtual potential temperature profiles and CO 2 gradients, compared to the free troposphere aloft, suggestive of a strong O 3 deposition over Siberian forests