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Zmienność przestrzenna występowania zim bezjądrowych na Antarktydzie w latach 1990-1999

Lipowska S.

Problemy Klimatologii Polarnej

2004

nr 14

19-28

Characteristic feature of the air temperature course over the year on the Antarctic is the winter warming known as a Coreless Winter effect (Hann 1909, Marsz 2000). This phenomenon is related to the specific atmospheric circulation, frequent advection of warm air masses from the oceans into the interior of the continent and entering of cyclones onto the Antarctic. The rise in temperature during the winter season occurred in the period 1990-1999 on all selected researched stations, however it didn't become visible every year (Table 2). Analysis of annual courses of air temperature in the particular years in the last decade of 20th century proved, that the occurrence of the Coreless Winters on the Antarctic is a repeated phenomenon, characterized by spatial and temporal variability. An example of annual courses of air temperature with the coreless effect in 1997 on selected stations is shown on Fig. 2. The least number of Antarctic stations with the winter warming were observed in 1992, when the phenomenon was merely recorded on the half of all selected stations (Fig. 3), whereas the greatest extent was stated in 1997, when it occurred on the 88% of all the stations. Extents in the occurrence of the kernlose winters on the Antarctic for the particular years during the decade 1990-1999 are shown on Fig.4. In respect of regional location there was stated the existence of interdependences in the periods in occurrence of the rises in temperature during the winter season within 4 typical regions of the Antarctic according to selected research stations: - on the Antarctic Peninsular - in the interior of the continent - on the coast in zone 030°W - 120°E - on the coast in zone 120°E -120°W The analysis of annual courses of air temperature in the years with coreless effect indicated, that the most often rise in air temperature in the winter season was observed on the stations on the coast in zone 120°E - 120°W of the Antarctic, whereas the most rarely it was noted on the Antarctic Peninsular. The rises in temperature were mostly observed on the whole continent in June which equals 45% of all the warmings noted in years 1990-1999 on every stations, and in July - 33%. The rises in temperature were the most rarely observed in August and occurred merely in 22% of all the warmings. The relative frequency [in %] of occurrence the rises in temperature in the winter season according to month's intervals for the particular regions of the Antarctic in the period 1990-1999 is shown on Fig. 5. The great spatial and temporal variability in occurrence of the Coreless Winters on the Antarctic observed during the last decade of 20th century may prove the existence of the considerable dynamics of the circulation factors, which determine the formation of this phenomenon.