Characterizing Blocking Mobility and Its Role in Northern Hemisphere Cold Extremes

Atmospheric blocking, conventionally studied as a quasi-stationary phenomenon, often exhibits zonal movement under the influence of factors like the background flow and retrograding Rossby waves. However, the impact of this mobility on cold extremes remains under-investigated. This study classifies atmospheric blocking events during the winters of 1979/80–2020/21 into westward-moving, eastward-moving, and quasi-stationary types to analyze their distinct impacts on surface air temperature by region.

Our results show that westward-moving blocks occurred most frequently over the western North Pacific, whereas quasi-stationary blocks were dominant in most other regions. In terms of duration, westward-moving blocks consistently persisted longer than the other types across all regions. Notably, these long-lasting, westward-moving events were closely associated with inducing strong cold waves in downstream areas during their dissipation phase. This is attributed to the enhanced advection of cold Arctic air by blocking-induced low-level wind anomalies. These characteristics were successfully reproduced in CESM1-LENS simulations, suggesting that a better understanding of blocking mobility can contribute to improving extreme cold surge prediction.