Speaking: Judah Cohen (Atmospheric and Environmental Research, Inc)
Observed fall Eurasian snow cover extent (SCE) anomalies were first linked with variability in the North Atlantic/Arctic Oscillation (N/AO) where above normal SCE was related to colder temperatures across the Northern Hemisphere continents. Subsequent studies demonstrated that above normal SCE favored tropospheric precursors to sudden stratospheric warming (SSWs) and subsequent tropospheric negative N/AO events. However, the relationship has weakened over the past decade in the observations and is weak to absent in most modelling studies complicating our understanding of snow climate coupling.
In a more recent study, we showed that Eurasian SCE is better linked to a lesser-known stratospheric polar vortex (SPV) disruption that involves wave reflection and stretching of the SPV that is related to ridging/high pressure coupled with above normal temperatures across Alaska and cold to even extreme cold across parts of Asia and North America east of the Rockies. Using both observational analysis and novel numerical modeling experiments, we showed that autumn SCE and Arctic sea ice trends can force observed increasing trends in SPV stretching and surface impacts. Our analysis provides a dynamical link between rapid Arctic change and extreme winter weather across large regions of the Northern Hemisphere. Given the link between SCE and SPV variability, SCE could be utilized in subseasonal to seasonal prediction in the winter months.