Emergence of Winter Large-Scale Transient Atmospheric Waves in the Northern Hemisphere

Transient atmospheric waves, which modulate the mid-latitude storm tracks, are projected to intensify over most of the mid-latitudes in Northern Hemisphere winter, but to emerge out of the internal variability only over Eurasia, implying localized climate change impacts over this region. This assessment, however, aggregates different length scales of the waves, thus not accounting for possible different wave responses over various scales. Here, by separating large and small scales, we find that throughout the mid-latitudes large-scale boreal winter transient atmospheric waves are projected to intensify and emerge from the internal variability over the 21st century. In North America, the North Atlantic and the North Pacific, it is the projected weakening of small-scale waves that obscures the emergence of the waves when pooling together all scales. Our analysis further suggests that the region-dependent changes in transient atmospheric waves are linked to the regional Arctic warming patterns.