Smoke transport and potential impacts from all observed pyroCb events in North America during 2013–2023

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Abstract. Pyrocumulonimbus (pyroCb) events provide an efficient pathway for wildfire smoke and combustion products to enter the Upper Troposphere and Lower Stratosphere (UTLS), where they are transported far from their source regions and perturb atmospheric composition, radiation, and dynamics. Although there are individual case studies, their cumulative transport behaviour over decadal time scales remains insufficiently characterized. Here, we investigate the short-, mid-, and long-range transport pathways, seasonal and regional variability, vertical structure, and residence characteristics of smoke from all observed North American pyroCbs during 2013–2023 using the Langley Trajectory Model, evaluated against satellite observations. Results show that smoke transport is influenced by source region, season, injection layer, and the evolving synoptic-scale circulation. Summer accounts for the majority of events, while Canadian pyroCbs occur more frequently than pyroCbs in the United States and dominate much of the UTLS and long-range trans-Atlantic transport. Canadian smoke is often transported along midlatitude pathways toward Europe, whereas U.S. pyroCbs more strongly contribute to lower-latitude short- and mid-range transport and to tropical transport pathways. Short- and mid-range tropospheric transport reveals persistent free- and upper-tropospheric downstream convergence regions, indicating areas where smoke may repeatedly influence clouds, radiation, weather-relevant conditions. In contrast, UTLS and stratospheric transport pathways exhibit faster and longer-range transport, including recurrent midlatitude, tropical, cross-hemispheric pathways. This study provides a decadal transport framework for interpreting how smoke injected by North American pyroCbs is subsequently redistributed. The results help connect pyroCb smoke with observed smoke signatures and atmospheric impacts, while supporting future model evaluation and mission planning.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.