Seasonal patterns and consistency of extreme precipitation trends in Europe, December 1950 to February 2008

Seasonal trends in extreme precipitation indices were investigated for 30 yr moving periods between December 1950 and February 2008. To update the 2008 to 2015 data, supplementary calculations were performed for >120 meteorological stations. A linear regression of the least squares method was used to calculate trend magnitudes. Trend significance was tested using the Mann-Kendall method. Changes in short-term trend frequency and temporal coherence were assessed. Extreme precipitation was defined as a daily amount exceeding the 95th percentile, calculated separately for each month and station using daily totals ≥1 mm. The spatial pattern of extreme precipitation trends varied by season. Significant extreme precipitation trends were rare, constituting approximately 25 to 30% of all analysed trends, and were seldom temporally coherent. Most of these significant trends were upward, except in summer, when a nearly equal frequency of positive and negative trends was found. Increases in the frequency and the total were a characteristic feature of extreme precipitation changes, particularly in winter. Seasonal variations in the spatial patterns of extreme precipitation trends may have resulted from seasonal changes in the prominence of the driving factors of precipitation. In spring, upward trends in Central and Western Europe were twice as frequent as the downward trends found primarily in Southern Europe. In summer, the percentages of significant downward trends in Western Europe and upward trends in Eastern Europe were similar. In autumn, a coherent decrease in extreme precipitation was clear in Central Europe. The spatial distribution of trend directions was the most consistent in winter

Long-Term Variability of Precipitation form in Hornsund (Spitsbergen) in Relation to Atmospheric Circulation (1979–2009)

The paper discusses the impact of the atmospheric circulation on the long-term variability of liquid, mixed and solid precipitation. The three precipitation forms were characterised by their totals, the number of days when they prevailed, and the contribution of each to the overall precipitation totals. Trends, as a background to further analysis, were calculated with regard to each characteristic of each precipitation form. The most significant increases were recorded in the contribution of liquid precipitation to the overall precipitation totals in September and in the mixed precipitation totals in December and November. Arctic Oscillation (AO) was found to have only a minor influence on the long-term variability of precipitation characteristics. The AO phase could to some degree account for the observed variation in the number of days with liquid precipitation. On the other hand, the direction of the local advection could account for considerably more of this variability and also the variability in liquid precipitation totals

Cloud cover over Spitsbergen and its relation to atmospheric circulation (1983-2015)

This paper discusses the cloud cover and its relation to atmospheric circulation over Spitsbergen during 1983-2015. It focuses on monthly and seasonal cloud covers and on the frequency of days with specific cloud cover (cloudless, clear, cloudy and completely overcast sky) and their relation to various circulation types. In the research period the cloud cover characteristics were differentiated over the island on both monthly and seasonal scales, and they strongly depended on the direction of air advection. The highest mean daily cloud cover was reported for circulation types with air advection from the south (S+SWc and S+SWa). The greatest variation in the cloud cover distribution was observed during the polar night (at Svalbard Lufthavn and Ny-Ålesund) or in the autumn (Hornsund). The long-term variability in the cloud cover significantly depends on the frequency of N+NEa type (negative correlation) and on S+SWc and W+NWc and Cc+Bc types (positive correlation), particularly in spring

Vertical climatic belts in the Tatra Mountains in the light of current

The paper discusses temporal changes in the configuration of vertical climatic belts in the Tatra Mountains as a result of current climate change. Meteorological stations are scarce in the Tatra Mountains; therefore, we modelled decadal air temperatures using existing data from 20 meteorological stations and the relationship between air temperature and altitude. Air temperature was modelled separately for northern and southern slopes and for convex and concave landforms. Decadal air temperatures were additionally used to delineate five climatic belts previously distinguished by Hess on the basis of threshold values of annual air temperature. The spatial extent and location of the borderline isotherms of 6, 4, 2, 0, and − 2 °C for four decades, including 1951–1960, 1981–1990, 1991–2000, and 2001–2010, were compared. Significant warming in the Tatra Mountains, uniform in the vertical profile, started at the beginning of the 1980s and led to clear changes in the extent and location of the vertical climatic belts delineated on the basis of annual air temperature. The uphill shift of the borderline isotherms was more prominent on southern than on northern slopes. The highest rate of changes in the extent of the climatic belts was found above the isotherm of 0 °C (moderately cold and cold belts). The cold belt dramatically diminished in extent over the research period

Frequency of Ice Days at Selected Meteorological Stations in Svalbard

The paper aims to present research into both the long-term variability in the ice days in Svalbard representing the Atlantic sector of the Arctic, and their relations to atmospheric circulation. Ice days are defined as days with a daily maximum temperature below 0°C (Tmax<0°C). They are considered to be amongst the most important indices of current climate change. All the available data on daily maximum air temperature from three Norwegian stations (Svalbard Airport (Svalbard Lufthavn), Bjørnøya and Hopen) and from the Polish Polar Station in Hornsund (SW Spitsbergen) have been employed. The relevance of atmospheric circulation to the frequency of the occurrence of ice days was evaluated by calculating the Spearman correlation coefficients between the frequency of ice days and three regional circulation indices: zonal westerly circulation index (W), meridional southerly circulation index (S) and index of cyclonicity (C). At all the stations the number of ice days exhibited significant decreasing trends in the period of 1979-2012

FREQUENCY OF ICE DAYS AT SELECTED METEOROLOGICAL STATIONS IN SVALBARD

The paper aims to present research into both the long-term variability in the ice days in Svalbard representing the Atlantic sector of the Arctic, and their relations to atmospheric circulation. Ice days are defined as days with a daily maximum temperature below 0°C (Tmax&lt;0°C). They are considered to be amongst the most important indices of current climate change. All the available data on daily maximum air temperature from three Norwegian stations (Svalbard Airport (Svalbard Lufthavn), Bjørnøya and Hopen) and from the Polish Polar Station in Hornsund (SW Spitsbergen) have been employed. The relevance of atmospheric circulation to the frequency of the occurrence of ice days was evaluated by calculating the Spearman correlation coefficients between the frequency of ice days and three regional circulation indices: zonal westerly circulation index (W), meridional southerly circulation index (S) and index of cyclonicity (C). At all the stations the number of ice days exhibited significant decreasing trends in the period of 1979-2012

Synoptic climatology of fog in selected locations of southern Poland (1966-2015)

This paper investigates fog frequency in southern Poland in relation to various topography (concave and convex forms) and atmospheric circulation types. It also discusses long-term variability in the annual and seasonal number of days with fog. Daily information on fog occurrence was taken from three high quality synoptic stations representing various landforms: Kraków-Balice (bottom of the hollow), Katowice-Muchowiec (Silesian Upland) and Bielsko-Aleksandrowice (summit of Carpathian Foothill). In the central part of southern Poland during the last 50 years (1966–2015) fog occurred on average during 53–67 days a year. The annual number of foggy days in Kraków (67 days) located in a structural basin was by 14–15 days higher than in Bielsko (53 days) situated in the Silesian Foothills. In the annual course, high fog occurrence (above 6 days per month) was observed from September to January, with the maximum in Kraków (10 days in October). At every station the monthly minimum of fog occurrence fell in July (2 days). In summer and spring the highest probability of fog occurrence was found on days with anticyclonic types and air advection from the northeastern (Na, NEa) and eastern (Ea, SEa) sectors. In autumn, a high probability was also found for the anticyclonic types with advection of air mass from the eastern and southern sectors. In the Carpathian Foothills (Bielsko) the probability of fog occurrence in winter was significantly enhanced only for the cyclonic types with air advection from the eastern sector (NEc, Ec, SEc) and nonadvective types Cc (cyclone centre) and Bc (cyclonic trough). Trends in the fog frequency were mostly insignificant. The only significant decreasing trend was found in Kraków on the annual scale and in summer when fog frequency was low

Frosty, Freezing and Severe Freezing Days and Their Synoptic Implications in Małopolska, Southern Poland, 1951–2000

This study discusses the occurrence of days with unique thermal characteristics for the period 1951–2000. The authors investigated longterm variability, probability of occurrence and synoptic conditions favourable to frosty (tmin≤0˚C ∧ tmax>0˚C), freezing (tmax<0˚C) and severe freezing (tmax<-10˚C) days at six stations in the southern part of Poland. The occurrence of frosty days is characterized by the highest diversity, both in spatial and temporal terms and these days depend on the landform to the highest degree. The number of freezing days ranged from 28–30 in the foothills of the Carpathians to 147 at 2000 m a.s.l. in the Tatra Mountains, with severe freezing days from ca. 2 to ca. 18 days respectively, though no distinct trends were noted in their long-term progression. The anticyclonic situations and air mass advection from the southern sector (frosty days), from the east, south-east and north (freezing and severe freezing days) were the most favourable for the days examined

The influence of synoptic situations on summer precipitation in urban area (Katowice) and at foreground of Beskid Śląski Mountains (Aleksandrowice)

Dokonano analizy wpływu sytuacji synoptycznych na pojawianie się letnich opadów atmosferycznych. Średni dobowy opad w całym wieloleciu 1966-1996 i w poszczególnych sezonach tego wielolecia nie jest doskonałą charakterystyką synoptyczno-klimatologiczną. W artykule określono również prawdopodobieństwo wystąpienia dni z opadem ~ 0,1 mm i ~ 10,0 mm dla całego okresu i dla poszczególnych sezonów. Dane pochodzą z serii pomiarów opadów w Katowicach i Aleksandrowicach.The analysis of influence of synoptic situations on appearance summer precipitation was made. Daily average precipitation in term 1966--1996 and in individual seasons of this term were imperfed synoptic-climatological characteristic. The possibility of appearance day with precipitation ~ 0,1 mm and ~ 10 mm in all analysed long-term and individual seasons was also made in this study. The data comes from Katowice's and Aleksandrowice's measurements series of precipitation.[443]-44

FROSTY, FREEZING AND SEVERE FREEZING DAYS AND THEIR SYNOPTIC IMPLICATIONS IN MAŁOPOLSKA, SOUTHERN POLAND, 1951–2000

This study discusses the occurrence of days with unique thermal  characteristics for the period 1951–2000. The authors investigated longterm  variability, probability of occurrence and synoptic conditions favourable  to frosty (tmin≤0˚C ∧ tmax&gt;0˚C), freezing (tmax&lt;0˚C) and severe freezing  (tmax&lt;-10˚C) days at six stations in the southern part of Poland. The occurrence  of frosty days is characterized by the highest diversity, both in spatial  and temporal terms and these days depend on the landform to the highest  degree. The number of freezing days ranged from 28–30 in the foothills of  the Carpathians to 147 at 2000 m a.s.l. in the Tatra Mountains, with severe  freezing days from ca. 2 to ca. 18 days respectively, though no distinct trends  were noted in their long-term progression. The anticyclonic situations and  air mass advection from the southern sector (frosty days), from the east,  south-east and north (freezing and severe freezing days) were the most favourable  for the days examined.