Abstract
Contribution of extra-tropical synoptic cyclones to the formation of mean summer atmospheric circulation patterns in the Arctic domain (≥60° N) was investigated by clustering dominant Arctic circulation patterns based on daily mean sea-level pressure using self-organizing maps (SOMs). Three SOM patterns were identified; one pattern had prevalent low-pressure anomalies in the Arctic Circle (SOM1), while two exhibited opposite dipoles with primary high-pressure anomalies covering the Arctic Ocean (SOM2 and SOM3). The time series of their occurrence frequencies demonstrated the largest inter-annual variation in SOM1, a slight decreasing trend in SOM2, and the abrupt upswing after 2007 in SOM3. Analyses of synoptic cyclone activity using the cyclone track data confirmed the vital contribution of synoptic cyclones to the formation of large-scale patterns. Arctic cyclone activity was enhanced in the SOM1, which was consistent with the meridional temperature gradient increases over the land–Arctic ocean boundaries co-located with major cyclone pathways. The composite daily synoptic evolution of each SOM revealed that all three SOMs persisted for less than five days on average. These evolutionary short-term weather patterns have substantial variability at inter-annual and longer timescales. Therefore, the synoptic-scale activity is central to forming the seasonal-mean climate of the Arctic.
Highlights
Low-frequency atmospheric circulation modes in the Arctic (e.g., the Arctic Oscillation (AO), Dipole Anomaly (DA), etc.) have attracted much attention owing to their role as controlling factors in the spatiotemporal sea-ice variability [1,2,3]
Studies have shown that the activity of synoptic cyclones is more prevalent during summer in the Arctic Ocean [13,14,15]; it has been suggested that they potentially contribute to seasonal-mean Arctic climate [13,14,20]
Our results add to literature on the quantitative contribution of synoptic cyclone activity to the amplitude of seasonal-mean anomalies in individual activity cores of the three dominant Arctic summer circulation patterns as clustered by the self-organizing maps (SOMs) method (Table 2)
Summary
Low-frequency atmospheric circulation modes in the Arctic (e.g., the Arctic Oscillation (AO), Dipole Anomaly (DA), etc.) have attracted much attention owing to their role as controlling factors in the spatiotemporal sea-ice variability [1,2,3] This role can be investigated by various methods based on relatively more abundant atmospheric data sources, instead of with the ocean circulation patterns. Oscillation (NAO), and their relative frequency occurrence, as compared to the EOFs. In addition, the SOMs have been used to distinguish patterns related to the variabilities of winter cold extremes over North America and Europe [25] and summer heat waves over the Northern Hemisphere [26].
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