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1 2003

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Wpływ Oscylacji Północnoatlantyckiej i Arktycznej na warunki termiczne chłodnej pory roku w Polsce w XVI - XX wiekach

Przybylak R., Wójcik G., Marciniak K.

Przegląd Geofizyczny

2003

Z. 1-2

61-74

The paper investigates the influence of the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) on thermal conditions in Poland from the 16lh to the 20th centuries. For this purpose the monthly (1659-1990) and seasonal (1500-1658) NAO and AO indices reconstructed by Luterbacher et a\. (1999, 2002) have been used. On the other hand, the winter climate in Poland was characterised: i) for the instrumental period using the recently homogenised air temperature series from Warsaw (Lorenc 2000), and ii) for the pre-instrumental period using reconstructions of: a) mean January-April air temperature based on dendrochronological data (Przybylak et al. 2001), b) winter (Dec-Feb) air temperature indices based on historical sources. The investigations of relationships between the circulation indices and winter climate in Poland were carried out separately for the entire series of data and for chosen years with the extreme high/low NAO and AO indices. It was shown that changes in atmospheric circulation explain about 25% of winter air temperature variation in Warsaw in the period from 1779 AD to 1990 AD. When the reconstructed series of mean January-April air temperature is used, the explained variances are significantly lower and oscillate from 2.2% for the first 300 years to 8.4% for the last 190 years. The worst results were obtained for the 17th century (ca 1%) and the best for the 20th century (ca 14%). The weaker relationships in the first 300 years are probably connected with the lower reliability of the NAO and AO reconstructions prior to 1800 AD. For the extreme NAO and AO years the relationships with the winter climate in Poland are significantly greater. The influence of atmospheric circulation was about twice as strong during negative phases of the NAO and AO indices in comparison with their positive phases. It has been also found that two-thirds of the cases with the annual extreme high/low tree-ring widths of the Scots pine (Pinus sylvestris L.) were noted during the occurrence of the positive/negative NAO and AO indices, respectively. In conclusion, the existence of not high, but statistically significant relationships between the NAO and AO indices on the one hand, and, on the other hand, winter climate in Poland in the pre-instrumental period, confirms that Luterbacher et al.'s reconstructions of the NAO and AO indices are quite good. Here we should add that the data from Poland have not been used for reconstructions of atmospheric circulation. However, our results also show that an improvement of these reconstructions for the first 300 years (and especially for the 17th century) is needed.