Wpływ cyrkulacji atmosferycznej na opady w Tatrach oraz Czarnohorze = Influence of atmospheric circulation on precipitation in Tatra and Chornohora Mts.

While significant increases in air temperature are being observed in the context of climate change, precipitation characteristics, indicators and indices seem to be changing in a more regionally-variable manner. High-mountain areas prove particularly subject to fluctuations and changes of climate, given that mountains serve as barriers to masses of air flowing over them, with the result that atmospheric precipitation totals are high in the context of the so-called orographic rainfall. Overall, the Chornohora represents the highest range anywhere in Ukraine’s Carpathian Mts, as there are six peaks over 2000 m a.s.l. capable of serving as a barrier running NW-SE. Nevertheless, the main ridge of the High Tatras (of the Slovakia-Poland borderland) is even higher and runs W-E. Each massif is some 30 km in length, while the two ranges are separated by a distance of almost 350 km. Main drainage divides run along the highest ridges here, with the Tatras separating the drainage basins of the Vistula and Danube, while the Chornohora represent a divide between the Prut and Tysa basins. The aim here has been to present characteristics of atmospheric precipitation in Tatra and Chornohora Mts. as these are seen to relate to atmospheric circulation. To this end, the dependent relationship between intensity of precipitation and atmospheric circulation was examined exhaustively, with changes in the latter considered from the point of view of intensity of precipitation in the massifs under study, and with trends for precipitation over the study period also looked for.The Niedźwiedź (2017) classification of types of atmospheric circulation was applied, with annual values calculated for circulation indicators P (a W-E inflow), S (a S-N inflow) and C (a cyclonic/anticyclonic inflow). Overall, the study drew on 1961‑2015 daily precipitation data from the north-eastern slope of Chornohora Mts. (as represented by Ukraine’s Pozhyzhevska weather station, PO, 1451 m a.s.l.), as well as the north slope of the Tatra Mts. (as represented by Poland’s Hala Gasienicowa weather station, HG, 1520 m a.s.l.).An air inflow from western directions was found to have prevailed over 28% of the days in the average year (Fig. 1). The most frequent types involved here were: Ka (12%), Bc (10%), Wc (10%) and Wa (8%). During the summer months (JJA), it is the Ka and Bc types that are even more frequent (present on approx. 15% of summer days). Types Wc and Wa in turn occur more frequently in winter (DJF) – respectively 13% and 12% of the time. In autumn, these types reach a level of occurrence around 10%.At 1712 mm, the average annual rainfall total for Tatra Mts is higher than that for the Chornohora (on 1446 mm). While the seasonal distribution of rainfall in spring and autumn looks almost the same in the two massifs, winter brings more precipitation in the Chornohora, while summer is a wetter season in the Tatras (Fig. 2). Largest amounts of precipitation nevertheless fall in the warm half-year, in the circumstances of N+NEa advection, cyclonic situations and under arctic, polar-marine or polar-marine transformed air masses (Figs. 3 and 4).The largest changes over time are to be observed for the zonal inflow index (P) and the cyclonic index (C). The P index points to increased numbers of days with a western circulation, while the C index confirms the domination of anticyclonic circulation (Fig. 5). The trend for annual rainfall totals is an upward one overall in both regions, but in neither does this achieve statistical significance (Fig. 6). Equally, there is a downward trend line for numbers of days featuring precipitation (RRdays) in the cases of both the Chornohora and Tatra ranges (equal to -7.3 days/10 years and -7.59 days/10 years respectively) (Fig. 7). On the other hand, the trend for numbers of days with higher rainfall, e.g. with RRdays>10mm is upward for the Chornohora (at +1.23 days/10 years), but downward for the Tatra Mts (at -0.6 days/10 years) (Fig. 8).