Robert Twardosz

Anomalously high monthly precipitation totals in the Polish Carpathian Mountains and their foreland (1881–2010)

The study addresses the problem of river flooding and other dangerous natural processes as well as phenomena resulting from persistent heavy rainfall. Annual and multi-annual records of anomalously heavy precipitation were investigated using data from 16 weather stations in the Polish Carpathian Mountains and their foreland from the period 1881–2010. The anomalously high precipitation was studied in terms of its annual and multi-annual pattern, time of occurrence, spatial extent and the coinciding atmospheric circulation. The anomalously high monthly totals were defined as those, which exceeded the upper quartile plus 1.5x the interquartile range. It was found that during the 130 years of the study period, there were 200 anomalously heavy precipitation months (AHMs), which occurred in 106 years. Most of them were only recorded at either a single station or at two neighbouring stations, which would suggest that precipitation of this magnitude depends not just on circulation circumstances, but also on local factors. No statistical change was found in the long-term A H M occurrence pattern. There were two instances, where an A H M was recorded simultaneously at all 16 stations, in May 1940 and 2010, and they both contributed to catastrophic floods. The latter of the events involved both the highest absolute totals (exceeding 500 mm) and the highest relative totals (i.e. the percentage of the long-term average close to 500%). The A H Ms tended to coincide with cyclonic circulation. Between October and March, this was the western cyclonic circulation ( Wc ), while for the remaining part of the year it was cyclonic trough (Bc).

Monthly thermal anomalies in the Mediterranean (1951–2010)

Abstract: The study determines the frequency of monthly thermal anomalies in the Mediterranean Basin (approx. south of 45oN), in the area from Lisbon in the west to Van in eastern Turkey, changes in the frequency of such anomalies over six decades, as well as the location and size of the area over which they occurred. The present study is based  on the average monthly air temperature values from 80 meteorological stations in the years 1951–2010. Thermally anomalous months are considered to have occurred when the average air temperature t at a given station differed from the corresponding tav. by at least 2 standard deviations (σ); for anomalously cold months (ACMs: t£tav.–2σ) and for anomalously warm months (AWMs: t≥tav.+2σ). One feature that distinguishes the Mediterranean Basin from the rest of Europe located in the temperate climate zone is the prevalence of AWMs over ACMs. The number of ACMs and AWMs showed significant variations over the 60-year period. The years 1971–1980 were the coldest ones, while the 21st century saw the highest temperatures. The vast majority of ACMs and AWMs occur over small areas. There were 22 anomalous months (11 ACMs and AWMs) that covered larger areas (at least 25% of the stations).

Keywords: contemporary warming, climate change, thermal anomalies, southern Europe

Zarys treści: Określono częstość miesięcznych anomalii termicznych w basenie Morza Śródziemnego, zmiany częstości anomalii w latach 1951–2010, ich lokalizację i zasięgi występowania. Podstawą opracowania są wartości średnie miesięczne temperatury powietrza z 80 stacji meteorologicznych z 60-lecia 1951–2010. Za miesiące anomalne pod względem termicznym przyjęto te, w których średnia temperatura t różniła się na danej stacji od odpowiedniej tśr. 60-letniej przynajmniej o 2 odchylenia standardowe (σ). Wyłoniono miesiące anomalnie zimne (MAZ: t£tśr.–2σ) i anomalnie ciepłe (MAC: t≥tśr.+2σ). Cechą wyróżniającą całego basenu Morza Śródziemnego od pozostałej części Europy, położonej w strefie klimatu umiarkowanego, jest przewaga częstości MAC nad MAZ. Liczba MAZ i MAC znacznie zmieniała się w ciągu 60-lecia. Najchłodniej było w latach 1971–1980, a najcieplej w XXI w. MAZ i MAC w ogromnej większości występują na małych obszarach. Tych, które pojawiają się na dużym obszarze (na przynajmniej 25% stacji), było 22 (po 11 MAZ i MAC).

Impact of atmospheric circulation on air temperature in Warsaw during months with extreme values of the NAO index (1951–2015)

In winter, western air masses arriving in Europe, including Poland, change the weather for relatively warmer, while an eastern advection tends to bring freezing temperatures. While the NAO provides a quantitative measure of this western advection, its relationship with air temperature is not always clear-cut. For this reason, this study characterises the circulation and thermal conditions over Poland depending on the sign and the value of the NAO index (NAO+, NAO–).
The study is based on NAO values and winter (December – March) monthly temperature records in Warsaw spanning 65 years (1951–2015), as well as on the calendar of circulation types proposed by Lityński. A detailed analysis was performed looking at the top 10 months with the highest NAO+ and NAO–, as well as the top 10 months with the greatest positive and negative deviations from the long-term average air temperature (Dt). This selection was based on a premise that the months should largely coincide. The results, however, show certain deviations from previously established patterns in the influence of the NAO+/NAO– on air temperature in Poland.

W artykule zbadano wieloletni i roczny przebieg najwyższych miesięcznych sum opadów atmosferycznych w Polskich Karpatach Zachodnich na podstawie danych z 6 stacji: Nowy Sącz, Sanok, Bielsko-Biała, Maków Podhalański, Krynica i Zakopane z okresu 1951–2005 oraz wyznaczono ich wartości prawdopodobne. Wykazano, że najwyższe miesięczne sumy opadów mogą występować w ciągu całego roku, z największą częstością w miesiącach letnich. Nie stwierdzono istotnych statystycznie trendów zmian wieloletnich, a jedynie krótkookresowe fluktuacje.