A composite-based analysis of the dynamical linkage of Atmospheric Rivers, Warm Conveyor Belts, and Extratropical Cyclones

Abstract. Extratropical cyclones (ETCs), warm conveyor belts (WCBs), and atmospheric rivers (ARs) are dynamically connected features key to understand midlatitude weather and hydroclimate. However, the precise spatial and temporal coupling between the moisture transport in ARs and the ascent in ETC’s associated WCBs remains poorly understood. Therefore, this study employs a composite-based analysis, combining probabilistic footprints of WCB identification and Eulerian AR detection for the North Atlantic extended winter (October–March) using ERA5 reanalysis. We evaluate composite fields relative to AR centroids, differentiating between events where the WCB ascent phase is present within the AR plume from those where it is absent. Our results demonstrate that ARs linked to WCBs are characterized by stronger integrated vapor transport, a wider AR plume, and, most critically, a shift of precipitation maxima northeast of the AR axis, aligning with the region of strongest frontal ascent near the associated ETC. In contrast, AR-only events exhibit weaker IVT values and a diffuse precipitation to the northeast towards the cyclone. Finally, temporal composites centered on the ETC's maximum deepening point (MDP) reveal a phased evolution: while peak WCB-inflow precedes the MDP, peak WCB-ascent and AR-related precipitation coincide with the MDP, and peak WCB-outflow follows, illustrating a tightly coupled feedback loop.