Abstract Warm conveyor belts (WCBs) are key ascending airstreams in extratropical cyclones that shape midlatitude moisture transport and precipitation. Here we show that WCB activity is tightly linked to the large-scale transformed Eulerian-mean (TEM) circulation in Northern Hemisphere winter. The climatological WCB frequency aligns with the rising branch of the TEM circulation, and the two exhibit strong day-to-day covariability. Variations in WCB activity correspond systematically to changes in large-scale eddy fluxes: enhanced eddy momentum flux (EMF) shifts WCB activity poleward through changes in ascent rate, while enhanced eddy heat flux (EHF) primarily strengthens WCB activity downstream over the Pacific, with little meridional displacement. WCBs account for up to 89% of EMF-related and 56% of EHF-related precipitation anomalies, with the exact fraction varying by latitude. These results demonstrate that the TEM framework provides insight into the zonal-mean imprint of WCB activity and associated precipitation, and how these relationships may change in the future.
Hwang et al. (Fri,) studied this question.