A B S T R A C TTo develop a 14-winter (OctoberÁApril; 1999Á2013) climatic description of polar low (PL) occurrence for the Nordic Seas, systems have been tracked using images acquired from the Very High Resolution Radiometer (AVHRR). Also, the dominant PL characteristics Á their temporal and spatial distributions, size, lifespan, distance travelled, speed of propagation and directions Á have been determined. On average, 14 PL events occur per winter but there is strong inter-annual and intra-seasonal variability. Although systems may form and travel over the whole Nordic Seas, their genesis is enhanced in areas characterised by warm oceanic currents. At the start of the season (OctoberÁNovember), systems mainly form over the Greenland and Norwegian Seas, but further into winter they form increasingly over the Barents Sea. In connection with recent low-ice winters, new areas of PL formation are evident, particularly to the west of Spitsbergen and in the Barents Sea. PL speeds of propagation range between 5 and 13 m/s but are observed to be highly variable among cases and even during the lifespan of individual PLs. To a considerable extent, the direction of movement is controlled by the large-scale flow in the lowest atmospheric layers, but we also observed cyclonic co-rotation of some pairs of PLs due to their influence on the ambient flow. Although these generally move southward or southeastward, a substantial number of PLs have westward and even northward tracks. PLs in the western part of the region average larger than their eastern counterparts. This study also highlights that PLs characteristics and tracks differ according to weather regimes.

Polar low (PL) storms are an important feature of the wintertime subsynoptic‐scale atmospheric circulation of middle‐ and higher‐latitude ocean areas. They can generate hazardous conditions impacting coastal and marine activities like fishing, transport, and oil extraction. However, there are few studies available of individual PL systems based on high‐resolution maritime surface data. Accordingly, the meteorological impacts of 29 PLs have been investigated for the 14 winters 1999–2013, using in situ measurements at eight stations in the Norwegian and North Seas. On average, the highest wind speed and significant wave height (SWH) occur following the minimum in sea level pressure of the PL, respectively, 1 and 3 hr after its passage. The strongest wind speed averages 17.1 m/s, and the highest peak SWH is 6.3 m, but these can reach 31 m/s and 11 m, respectively. PL characteristics of system horizontal extent, propagation speed, and the larger‐scale atmospheric circulation environment explain the large intercase differences. Large, multiple, and fast‐moving PLs within a meridional circulation environment appear to generate stronger near‐surface winds and higher waves than do small, single, and slow‐moving PLs within a zonal circulation. Multiple systems may have the largest impacts (e.g., SWH > 8 m), although a larger sample size is required to confirm this possibility. The impacts of PLs on sea surface temperature (SST) are quite small and are difficult to interpret separate from the background SST variation. The observed SST decrease may be mainly caused by the cold air outbreak within which the PL is embedded; indeed, a positive SST minus air temperature anomaly is found during the 24 hr preceding the passage of PL vortices, indicating enhanced low‐level atmospheric instability.

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