Winter lightning and north Atlantic oscillation

The relationship between the North Atlantic Oscillation (NAO) and total (in cloud and cloud to ground) lightning activity during the wintertime (December to March) is analyzed. Lightning data from the Optical Transient Detector were used and were studied in the North Atlantic and western European area. The southern half of the area analyzed (latitudes lower than similar to 50 degrees N) was observed to have an increased (decreased) lightning flash rate associated with negative (positive) NAO index values. The opposite relationship was found when the northern half (latitudes higher than similar to 50 degrees N) was considered. In both cases, the effect of the NAO on the lightning activity was stronger over the eastern area analyzed. Low (clearly <1) absolute values of the NAO index seem to be associated with minimum lightning activity.