Abstract. This paper analyses a stratospheric injection by deep convection of biomass fire emissions over North America (Alaska, Yukon and Northwest Territories) on 24 June 2004 and its long-range transport over the eastern coast of the United States and the eastern Atlantic. The case study is based on airborne MOZAIC observations of ozone, carbon monoxide, nitrogen oxides and water vapour during the crossing of the southernmost tip of an upper level trough over the Eastern Atlantic on 30 June and on a vertical profile over Washington DC on 30 June, and on lidar observations of aerosol backscattering at Madison (University of Wisconsin) on 28 June. Attribution of the observed CO plumes to the boreal fires is achieved by backward simulations with a Lagrangian particle dispersion model (FLEXPART). A simulation with the Meso-NH model for the source region shows that a boundary layer tracer, mimicking the boreal forest fire smoke, is lofted into the lowermost stratosphere (2-5 pvu layer) during the diurnal convective cycle at isentropic levels (above 335 K) corresponding to those of the downstream MOZAIC observations. It is shown that the order of magnitude of the time needed by the parameterized convective detrainment flux to fill the volume of a model mesh (20 km horizontal, 500 m vertical) above the tropopause with pure boundary layer air would be about 7.5 h, i.e. a time period compatible with the convective diurnal cycle. Over the area of interest, the maximum instantaneous detrainment fluxes deposited about 15 to 20% of the initial boundary layerCorrespondence to: J.-P. Cammas (jean-pierre.cammas@aero.obs-mip.fr) tracer concentration at 335 K. According to the 275-ppbv carbon monoxide maximum mixing ratio observed by MOZAIC over Eastern Atlantic, such detrainment fluxes would be associated with a 1.4-1.8 ppmv carbon monoxide mixing ratio in the boundary layer over the source region.

Global Positioning System (GPS) Radio Occultation (RO) observations aboard Low Earth Orbiting (LEO) satellites provide a powerful tool for global atmospheric sounding. Activated almost continuously since mid-2001, the CHAMP (CHAllenging Minisatellite Payload) GPS RO experiment provides up to 200 vertical atmospheric profiles per day. In this study we intercompare CHAMP RO humidity results and analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) with coinciding MOZAIC (Measurement of OZone and water vapour by AIrbus in-service airCraft) data collected during aircraft ascents and descents. About 320 coinciding profiles with CHAMP were found from 2001 until 2006 (coincidence radius: 3 hours, 300 km). Between about 650 and 300 hPa the CHAMP-MOZAIC humidity bias is smaller than the ECMWF-MOZAIC bias. On the other hand, the standard deviation between MOZAIC and CHAMP humidity is slightly higher than between MOZAIC and ECMWF through the entire altitude range. Apart from the water vapour validation (ascent and descent data), we also compare MOZAIC cruise data at typically 10-11 km altitude with CHAMP refractivity and temperature results (dry retrieval) and corresponding ECMWF analysis data. Whereas refractivity data from MOZAIC, CHAMP and ECMWF show excellent agreement, the CHAMP temperature exhibits a cold bias of about 0.9 K in comparison to MOZAIC and ECMWF.