Zróżnicowanie opadów atmosferycznych w rejonie Kaffioyry (NW Spitsbergen) w sezonie letnim w latach 1980-2008

W opracowaniu przedstawiono zróżnicowanie warunków opadowych w rejonie Kaffioyry (NW Spitsbergen) w sezonie letnim na podstawie danych z lat 1980-2008. Zbadano wpływ cyrkulacji atmosferycznej i warunków lokalnych na opady atmosferyczne. Uzyskane wyniki porównano ze stacją Ny-Alesund.

Precipitation in the Arctic, including Spitsbergen, is very important for both the biosphere and for the mass balance of glaciers. Our knowledge about its values inside Arctic islands is limited because almost all meteorological stations are located on tundra below 200 m a.s.l. Therefore any information about precipitation conditions occurring on glaciated and non-glaciated areas lying in the inner parts of Spitsbergen is very valuable. In this paper we present results of precipitation measurements carried out in north-western Spitsbergen (the Kaffioyra region and the Ny Alesund station) in selected summer seasons during the period 1980-2008. Precipitation measurements in the Kaffioyra region have been done during Toruń Polar Expeditions in three stations (base station – Kaffioyra-Heggodden (KH) and two glacier stations located in the lower part (LW1) and upper part (LW2) (see Figure 1 and Table 1). Data for the Ny Alesund (NA) station were obtained from the Norwegian Meteorological Institute. In the KH and NA stations measurements were recorded every day, while in LW1 and LW2 they were generally taken every 1-2 days. Results of precipitation conditions are presented for a common period of observations, i. e. for 21st July-31st August. The influence of atmospheric circulation on precipitation was investigated using the catalogue of circulation types constructed by Niedźwiedź (2009). In the summer season precipitation is greater at the end of the study period, than at the beginning. Year-to-year variability of summer precipitation totals is very large. For example, in KH, the highest precipitation (122.5 mm) occurred in 1997, while the lowest (12.3 mm) was in 2007 (Table 2). Also, the frequency of daily precipitation (.0.1 mm) is significantly greater in most wet summer (61.9%) than in most dry summer (28.6%) (see Table 3). Daily precipitation of .10 mm is rare in the KH station and occurred in only 4 out of the 12 summer seasons. It is well known that precipitation is greater in the inner parts of Spitsbergen than in tundra areas. Less is known, however, about the magnitudes of these differences. For the Kaffioyra region precipi-tation observations are available for 9 summer seasons (Tables 5 and 6). From these Tables and Figure 2 it is clear that precipitation on glaciers is almost always greater than in tundra. On average, summer precipitation totals are greater in LW1 and LW2 than in KH by 21.5 and 35.1 mm, respectively. The greatest differences occurred in 1980, while the lowest were in 2007, when even in LW1 precipitation was lower than in KH (Table 5, Figure 3). Lapse rates of precipitation in the Kaffioyra region are greatest between tundra and glaciated areas (oscillating between 13.2mm/100m and 18.5mm/100m between KH and LW2 and KH and LW1, respectively (Table 7)). On the other hand, this lapse rate between stations LW1 and LW2 is the lowest (only 10.7 mm/100 m). Correlation coefficients of 10-day precipitation totals between the meteorological stations in the Kaffioyra region are very high and exceed 0.9. The greatest precipitation in the Kaffioyra region occurred during the inflow of air masses from the southern sector (Table 8, Fig. 7).