Climatology of polar lows over the Norwegian and Barents Seas

The large-scale flow pattern during the formation of polar lows over the Norwegian and Barents Seas has been studied. The results indicate that in most cases a strong northerly airflow is located close to the east coast of Greenland. The geographical distribution of polar lows suggests a division of the events into two groups, a western group consisting of the lows first observed west of 5°E, and an eastern group consisting of those first observed east of the same longitude. Mean maps for each group were constructed for the winter season, and they show large anomalies. The strongest negative anomaly in the 500 mb height is found over the Norwegian Sea. The anomaly is – 230 gpm for the events west of 5°E, and – 179 gpm for those east of 5°E. For polar lows developing in the western sector, the largest positive anomaly, + 198 gpm, is associated with the Azores High. When polar lows are formed in the eastern sector, the strongest positive anomaly is associated with the ridge over Greenland; the cold air in the strong northerly flow east of Greenland is then up to 8°C colder than normal. The location of this cold anomaly gives a westward tilt of the anomaly pattern with height.