Adam Mickiewicz University in Poznań, Institute of Physical Geography and, Environmental Planning
Department of climatology - Poland
The aim of the study was to fined out co-relation between fluctuation of atmosphere circulation above the North Atlantic and Europe, defined by the NAO index figure, and thunderstorms occurring in Poland in winter and summer months. When analyzing the above issue the following have been taking into consideration: data captured in 17 weather monitor stations located within the Polish territory and working within IMGW structure (Institute of Meteorology and Water Economy) on thunderstorms occurred in years from 1969 to 1998, the NAO index figures calculated by J. Hurrel and air flows directions incoming to Poland in the examined 30 - years' period.
In the summer period (months from June to August) a poor negative correlation between the NAO index figure and number of days with thunderstorm has been acknowledged. In the winter period (months from December to February) in a vast number of station a positive correlation between the NAO index figure and numbers of thunderstorms have been found. February has attracted a special attention as in that month all thunderstorms have appeared only at times of very high positive numbers of the NAO index figure.
A strong positive co-relation between the NAO index figure and the air flowing to Poland from the west area sector (NW, W and SW) has been noticed in the whole winter period and especially in February. The research results indicate that the positive phase of the NAO resulting in appearance of warm and wet winters in Europe may also influence development of thunderstorm phenomena. In the summer months the co-relation between occurrence of thunderstorms and the NAO phenomenon is rather poor.