TRAILS – a novel framework for time-height-resolved attribution of long-range transported wildfire smoke

Abstract. Accurately attributing long-range transported wildfire smoke to specific sources remains challenging, especially for elevated plumes. This study presents the TRAILS tool (Trajectory-based Identification of Lofted Smoke), which extends the automated air mass source attribution tool of Radenz et al. (2021) to provide time- and height-resolved identification of wildfire smoke. By integrating 10-day backward trajectories from FLEXPART with a multi-sensor satellite detection algorithm, we calculate a vertically resolved Smoke Occurrence Fraction (SOF), quantifying the likelihood of smoke influence based on air parcel residence time within smoke-affected regions. TRAILS identifies where and at what altitudes smoke is present, but does not automatically attributes these layers to specific fire sources. A key innovation is a new, statistically significant linear relationship between Ozone Mapping and Profiler Suite (OMPS) Ultraviolet Aerosol Index (UVAI) values and smoke plume height for fresh tropospheric smoke, derived from collocated OMPS and CALIOP observations. TRAILS was evaluated against ground-based fluorescence lidar measurements (MARTHA and PollyXT in Leipzig during the 2023 Canadian wildfire season. Results show that TRAILS effectively reproduces the vertical distribution and temporal evolution of long-range smoke layers, with a 76 % detection rate for fluorescent aerosol layers. Systematic underestimation of layer heights by 0.4 km, most pronounced in the UTLS, is consistent with unaccounted diabatic self-lofting in FLEXPART. While TRAILS performs well for the Northern Hemisphere smoke events studied here, its application to other wildfire regimes (e.g., Southern Hemisphere, different fuel types) may require recalibration of thresholds and carries additional uncertainties related to dust contamination. TRAILS provides a valuable, observationally constrained method for time-height-resolved smoke attribution, particularly where advanced fluorescence lidars are unavailable.