Changes in thunderstorm activity at high latitudes observed at WMO weather stations

Abstract

Knowledge about the occurrence of thunderstorms in polar regions is still limited. Lightning detection systems have varying detection efficiency over time and space, which makes climatological analysis difficult. This is especially problematic in areas where lightning strikes are relatively rare. Traditional observations carried out at weather stations are therefore still a very important source of information about the occurrence of thunderstorms in the polar and circumpolar regions. Scientific studies usually predict that these phenomena will be more frequent in high latitudes in a warmer world. To check whether the number of thunderstorms changes as projected, we summarize SYNOP data from manned World Meteorological Organization (WMO) stations operating in the years 2000-2019 located at latitudes above 60° of both hemispheres. According to this source, the changes in thunderstorm frequency are only visible in certain areas and mostly during the summer months. The regional Kendall test revealed a statistically significant increase in the number of thunderstorm days north of 60°N in Interior Alaska, northwestern Canada, much of Siberia and European Russia. However, a decrease in thunderstorm frequency has also been detected in some regions. This was the case on the shores of the southern Norwegian Sea and seasonally in spring in the northern Urals. The largest increase in thunderstorm days exceeded 5 per decade in the highly continental regions of central Siberia and interior Alaska. For the entire high-latitude area, the change in the number of days with thunderstorms was statistically insignificant. However, the statistically relevant increase in the number of thunderstorm days is visible for inland weather stations located 250 – 1,000 km from the coastline, where it was on average 1 day per decade.