Fig. 1: North Atlantic winter storm tracks and Arctic entry rates stratified by the Arctic Oscillation (AO) index. | npj Climate and Atmospheric Science

Fig. 1: North Atlantic winter storm tracks and Arctic entry rates stratified by the Arctic Oscillation (AO) index.

From: Enhanced persistence of Ural blocking under strong positive AO: the role of North Atlantic storm tracks and potential vorticity dynamics

Fig. 1: North Atlantic winter storm tracks and Arctic entry rates stratified by the Arctic Oscillation (AO) index.The alternative text for this image may have been generated using AI.

Individual storm trajectories are shown for four AO regimes defined by the AO magnitude at each storm's peak intensity date: a AO Index >+1 σ, b 0 < AO Index ≤ +1 σ, c AO Index <–1 σ, and d –1 σ ≤ AO Index < 0. Here, 1 σ corresponds to the wintertime (DJF) standard deviation of the daily AO index (approximately 1.95). Each line represents an individual storm track, with shades of gray indicating storm intensity percentiles based on central pressure, where darker lines denote stronger cyclones (as indicated in the legend). The red dashed circle marks the Arctic domain (≥60°N). The percentage in the top-right of each panel indicates the fraction of storms that entered the Arctic under each AO regime. e Storm frequency binned by AO index magnitude (0.2 intervals), where gray bars represent the total number of storms and yellow bars indicate the number of Arctic-entering storms (≥60°N). The red dashed line shows the corresponding Arctic-entering ratio (%). Vertical dashed lines in (e) mark the +1 σ and −1 σ thresholds.

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