Open Geosci. 2016; 8:593–605

Research Article Open Access

Dragan D. Milošević*, Stevan M. Savić, Milana Pantelić, Uglješa Stankov, Igor Žiberna, Dragan Dolinaj, and Igor Leščešen Variability of seasonal and annual precipitation in and its correlation with large-scale atmospheric circulation

DOI 10.1515/geo-2016-0041 1 Introduction Received April 3, 2015; accepted December 17, 2015

Abstract: This paper examines temporal and spatial vari- Precipitation is a very important meteorological element ability and trends of annual and seasonal precipitation in in the Mediterranean (MR) as its future change can Slovenia and their relationship with three atmospheric cir- impact human activities (e.g. water management, agricul- culation patterns represented by their indices: North At- ture) and ecosystems. Significant progress has been made lantic Oscillation index (NAOi), Mediterranean Oscillation on projections for the MR [1]. Future projections re- index (MOi) and Western Mediterranean Oscillation index garding seasonal precipitation show predominant reduc- (WeMOi). Data from 45 precipitation stations were used tions for spring, summer and autumn, however projec- for the period 1963–2012. Mean annual precipitation varies tions for winter are distinctly different [2]. Precipitation is from 736 mm in eastern Slovenia to 2,518 mm in north- projected to decrease in all parts and all seasons (the most western Slovenia. A significant annual precipitation de- significant percent change occurs in summer) except for crease (from −3% to −6% per decade) is observed in west- the northernmost parts in winter [3]. This is in accordance ern Slovenia. Significant negative trends are observed in with the expected drying over the MR as a part of global southwestern Slovenia in summer (from −4% to −10% per warming [4]. decade) and near the Adriatic coast in spring (from −6% to Precipitation variability and trends in the MR have −10% per decade). Non-significant negative and positive been analyzed in many studies. For example, Ziv et al. [5] trends are observed in winter and autumn, respectively. analyzed changes in the precipitation regime of Israel Results indicate significant correlations between winter showing a statistically non-significant decreasing trend precipitation and MOi (from −0.3 to −0.7), NAOi (from prevailing in most of the country. The majority of Is- −0.3 to −0.6) and WeMOi (from 0.3 to 0.6). Significant We- rael has significant precipitation decrease only during MOi influence is observed in spring and autumn, while spring. Luković et al. [6] examined spatial patterns of rain- NAOi and MOi influence has not been detected. Annual fall trends in Serbia suggesting only weak, mostly non- precipitation and WeMOi are significantly correlated in significant trends. The study of de Luis et al. [7] has shown central and eastern Slovenia, while significant NAOi and a significant annual precipitation decrease in northwest- MOi influence is observed in western Slovenia (with the ern and western Slovenia and during all seasons, except larger area covered by MOi influence). autumn. As local changes in meteorological variables in mid- Keywords: precipitation; atmospheric circulation; North latitudes are mainly controlled by atmospheric circula- Atlantic Oscillation; Mediterranean Oscillation; Western tion [8, 9], the correlations between circulation indices Mediterranean Oscillation; Slovenia

Uglješa Stankov: Center for Spatial Information of Vojvodina *Corresponding Author: Dragan D. Milošević: Climatology and Province, Faculty of Science, University of Novi Sad, Trg Dositeja Hydrology Research Centre, Faculty of Science, University of Novi Obradovia 3, 21000 Novi Sad, Serbia Sad; Trg Dositeja Obradovića 3, 21000 Novi Sad, Serbia, E-mail: Igor Žiberna: Department of Geography, Faculty of Arts, University [email protected] of Maribor, Koroška cesta 160, Maribor, Slovenia Stevan M. Savić, Milana Pantelić, Dragan Dolinaj: Climatology Igor Leščešen: Department of Geography, Tourism and Hotel Man- and Hydrology Research Centre, Faculty of Science, University of agement, Faculty of Science, University of Novi Sad; Trg Dositeja Novi Sad; Trg Dositeja Obradovića 3, 21000 Novi Sad, Serbia Obradovića 3, 21000 Novi Sad, Serbia

© 2016 Dragan D. Milošević et al., published by De Gruyter Open. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License. 594 Ë Dragan D. Milošević et al. and precipitation in the MR are very important to analyze. The Republic of Slovenia is situated in the central- The relationships between atmospheric circulation pat- southern part of Europe (Figure 1) abutting four distinct tern indices and precipitation in Slovenia have not been geographical : the , the , the well identified: only a few studies [10, 11] have been made Dinaric Alps and the [22]. Slovenia ex- on this topic with only a limited number of precipitation tends between 45°25’ and 46°30’ N and 13°23’ and 16°36’ stations investigated. One of the goals in this paper is to an- E [23] and covers an area of 20,273 km2 [22] with a pop- alyze these relationships in order to obtain a better under- ulation of 2.06 million. The Alpine macroregion is in the standing of the causes of precipitation variability in Slove- north of Slovenia, while the Mediterranean macroregion nia. The study includes data on the large-scale North At- is in the west of Slovenia. Toward the east, the Mediter- lantic Oscillation (NAO) and regional Mediterranean and ranean macroregion is replaced by the Dinaric macrore- Western Mediterranean Oscillations (MO and WeMO, re- gion that stretches in a northwest-southeast direction and spectively) known to affect the MR. covers most of the southern part of Slovenia. The Pannon- NAO is associated with a meridional dipole structure ian macroregion is a densely populated and intensively in sea level pressure with two centers of action located cultivated area at the east end of Slovenia [24] (Figure 1). near Iceland and the Azores [12]. A positive NAO phase Submediterranean, temperate continental and alpine cli- leads to more intense precipitation over northern Europe, matic influences intertwine in the territory of Slovenia. whereas a negative NAO phase causes a precipitation shift However, most of Slovenia has a temperate continental towards southern Europe [8]. The influence of NAO on pre- climate. Alpine climate characterizes higher and lower cipitation in the MR has been investigated by a number of mountain areas to the north and west of the country, while authors [5, 8, 10–14]. A study by Sušelj and Bergant [11] a submediterranean climate is present in the south and showed significant negative correlation between NAOi and southwest of the country at the Adriatic coast (coastal sub- precipitation in Slovenia. However, this interpretation is mediterranean climate) and its hinterland (inland sub- limited by the fact that only four selected meteorological mediterranean climate). Continental climate intensifies stations represented the whole country which is geomor- with the distance increase from the and Alps- phologically and climatologically diverse. Dinaric mountain barrier towards the eastern and north- MO was defined in order to explain opposing atmo- eastern Slovenia [25]. spheric dynamics between the western and eastern part In the study of de Luis et al. [7] it was discussed that of the Mediterranean basin. The original MOi was defined changes in large-scale atmospheric circulation patterns as normalized pressure difference between Algiers and may have contributed to an observed long-term drying in Cairo [15]. A second version of this index, which was used Slovenia. This study contributes to the investigation of in this paper, can be calculated as the difference of stan- these suggested relationships. The main goals of this pa- dardized pressure anomalies at and the Israeli per are to investigate temporal and spatial variability and meteorological station of Lod [16]. The influence of MO trends of annual and seasonal precipitation in Slovenia on precipitation variability has been analyzed in numer- and to correlate them with indices of the large-scale (NAOi) ous studies [5, 10, 11, 13, 17–19]. A study of Sušelj and and regional (MOi and WeMOi) atmospheric circulation Bergant [11] showed significant negative correlation be- patterns, which are more representative for MR precipita- tween MOi and precipitation in Slovenia as registered at tion. four selected meteorological stations (, Murska Sobota, Rateče and Postojna). WeMO was defined by Martin-Vide and Lopez- 2 Data and methods Bustins [20] by means of the dipole composed by an an- ticyclone over the Azores and a depression over Liguria. Annual and seasonal precipitation in Slovenia recorded at This is the situation with a WeMO positive phase, while 45 stations was analyzed (Figure 1, Table 1). Selected pre- in the negative phase the situation is the opposite. We- cipitation stations are located on the territory of each of the MOi was defined as the result of the difference between different geographical regions of Slovenia: 16 in the Alpine standardized values in surface atmospheric pressure in macroregion, 15 in the Dinaric macroregion, 10 in the Pan- San Fernando (Spain) and Padua (). WeMOi’s influ- nonian macroregion and 4 in the Mediterranean macrore- ence on climate variability in the Iberian Peninsula has gion. Selection of adequate stations was based on the data been analyzed by Martin-Vide and Lopez-Bustins [20] and availability and homogeneity as well as macroregions’ av- Martin-Vide et al. [21]. erage size and altitudes. Variability of seasonal and annual precipitation in Slovenia Ë 595

Table 1: List of stations included in this study.

Station Latitude Longitude Altitude (m) Bilje (BLJ) 45°54’ 13°38’ 55 Brege (BG) 45°55’ 15°30’ 150 Dobliče (Črnomelj) (DO) 45°34’ 15°09’ 157 Morsko (MK) 46°05’ 13°38’ 170 Bizeljsko (BZ) 46°01’ 15°42’ 179 Murska Sobota (MS) 46°39’ 16°11’ 188 (LD) 46°34’ 16°28’ 195 Dvor (DV) 45°48’ 14°48’ 203 Novo Mesto (NM) 45°48’ 15°11’ 220 Laško (LS) 46°09’ 15°14’ 223 Ptuj (PT) 46°26’ 15°54’ 235 Celje (CLJ) 46°15’ 15°15’ 240 Mokronog (MO) 45°57’ 15°09’ 251 Fužina (FZ) 45°52’ 14°50’ 264 Maribor-Sabor (MB) 46°32’ 15°39’ 275 Ljubljana-Bežigrad (LJB) 46°04’ 14°31’ 299 Veliki Dolenci (VD) 46°50’ 16°17’ 308 Kadrenci (KC) 46°34’ 15°57’ 316 Godnje (GD) 45°45’ 13°51’ 320 Slovenske Konjice (SK) 46°20’ 15°26’ 332 Škofja Loka (SL) 46°10’ 14°18’ 340 Poljane (Škofja Loka) (PLJ) 46°07’ 14°11’ 385 Kranj (KA) 46°14’ 14°22’ 395 Gornji Grad (GG) 46°18’ 14°50’ 428 Kotlje (KT) 46°31’ 14°59’ 450 Bukovščica (BU) 46°14’ 14°16’ 458 Kočevje (KO) 45°39’ 14°51’ 467 Kozina (KZ) 45°36’ 13°56’ 490 Postojna (PO) 45°46’ 14°12’ 533 Podgrad (PR) 45°32’ 14°09’ 560 Sodražica (SO) 45°46’ 14°39’ 560 Cerknica (CK) 45°48’ 14°22’ 576 Mislinja (MI) 46°27’ 15°13’ 589 Šmarata (SM) 45°41’ 14°29’ 590 Črni Vrh (Idrijp) (CV) 45°56’ 14°03’ 683 Jurišče (JU) 45°40’ 14°18’ 703 Rut (RU) 46°12’ 13°54’ 710 Zgornja Radovna (ZR) 46°25’ 13°56’ 750 Jelendol (JD) 46°24’ 14°21’ 760 Kranjska Gora (KG) 46°29’ 13°48’ 804 Hrib (HB) 45°42’ 14°36’ 825 Rateče-Planica (RT) 46°30’ 13°43’ 864 Javorniški Rovt (JR) 46°28’ 14°06’ 940 Lokve (LO) 46°01’ 13°47’ 965 Planina pod Golico (PG) 46°28’ 14°03’ 970 596 Ë Dragan D. Milošević et al.

MOi). Monthly NAOi values were obtained from the Na- 160’0"E VD !

160’0"E tional Oceanic and Atmospheric Association (NOAA) Cli- 160’0"EMSMS Alpine ! 150’0"E KC macroregion ! LD! KT MB mate Prediction Center (CPC) website [31]. Daily values 140’0"E ! ! ! RT ! KG ! ! MI JR ! PT ! PG ! ZR ! JD SK of MOi were obtained from Climatic Research Unit web- GG ! ! BU CLJ 160’0"E RU ! ! KA ! ! LS site [32]. Monthly WeMOi data were obtained from the Uni- ! PLJ SL ! ! Pannonian ! MK LJB ! macroregion LO ! BZ ! 460’0"N 460’0"N versity of Barcelona website [33]. Annual and seasonal CV MO ! BG BLJ ! ! FZ ! ! CK DV NM NAOi and WeMOi were calculated using monthly series, GD PO ! SO ! ! ! ! ! Mediterranean JU SM ! HB ! ! KO macroregion ! KZ while annual and seasonal MOi were calculated using ! DO PR ! ! 140’0"E Dinaric macroregion 150’0"E daily series.

Station ! The spatial distribution of the results is displayed us-

Sources: Esri, DeLorme, NAVTEQ, TomTom, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, ing spatial interpolation (an ordinary Kriging method) of GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China 0 50100 km (Hong Kong), swisstopo, and the GIS the observed precipitation and precipitation trends for the 45 stations using the geostatistical software package AR- CGIS 10.1 with the Geostatistical Analyst Extension. Figure 1: Geographical location of the Republic of Slovenia in Eu- rope and the precipitation stations in the Republic of Slovenia.

The investigated period is from 1963 to 2012. Precip- 3 Results itation amounts were obtained from the Environmental Agency of the Republic of Slovenia (EARS). Winter (DJF), 3.1 Results of homogenisation spring (MAM), summer (JJA) and autumn (SON) precip- itation were calculated for each station using the stan- During the homogeneity testing of precipitation, the de- dard seasons definition. Winter precipitation corresponds tected break points were compared to metadata records to January-February of the calendar year and to December in order to diagnose the causes of any observed inhomo- of the previous year, while precipitation for other seasons geneity [34]. This type of information was crucial for apply- corresponds to the months from the calendar year. ing calculated corrections to the investigated series [35]. A standard Normal Homogeneity Test (SNHT) was ap- In most cases, the break points were related to the relo- plied for the detection of abrupt homogeneity breaks [26] cation of a station. From 45 stations used in the paper, in monthly precipitation values. The test is based upon the 23 were relocated during the investigated period. For in- assumption that the difference between precipitation se- stance, most breaks happened at the station Kozina (KZ) ries at a candidate station (the one being tested) and the (26 breaks) which was relocated four times during the re- reference series is fairly constant in time. Reference se- search period. In other cases, breaks were related to miss- ries were chosen from 4 to 6 stations, based on distance, ing values. 22 stations had missing values, but they did not similar altitude and squared correlation coefficient from exceed 5% of each station dataset. After a series of individ- 0.3 to 0.8 with the test station. The critical level of this ual or multiple homogeneity adjustments [36] conducted test was 95% [27]. Inhomogenieties were detected and cor- within this study, the series were considered to be homo- rected [28]. geneous. The adjustment values of the monthly time series Simple linear regression was used for obtaining an- usually ranged from −5 to 5 mm. nual and seasonal precipitation trends, while a Mann- Kendall nonparametric statistical test [29] was used to demonstrate the statistical significance of trends [30]. 3.2 Precipitation and precipitation regimes Statistical significance was defined at the level of95% and 99%. Rates of precipitation changes are expressed The highest annual precipitation amounts (>2400 mm) as %/decade, due to the differences in total precipitation were registered at stations located in the northwestern, amounts between regions [7]. mountainous part of Slovenia, influenced by interaction In order to understand Slovenian precipitation and its between alpine and submediteranean air masses. Towards relationship with atmospheric circulation patterns better, the east, continental climate influence prevails with the indices were examined using correlation analysis. Pear- lowest precipitation amounts recorded in the northeast- son’s correlation was used to reflect the degree of lin- ern, Pannonian part of the country (<800 mm) (Figure 2a). ear relationship between the precipitation and the atmo- spheric circulation pattern indices (NAOi, MOi and We- Variability of seasonal and annual precipitation in Slovenia Ë 597

Figure 2: Spatial distribution of mean precipitation amounts (mm) (a - annual; b - winter; c - spring; d - summer; e - autumn) in Slovenia during the 1963-2012 period.

During winter, the highest precipitation amounts are 250 mm and is influenced by temperate continental cli- registered at stations located in the northwestern, moun- mate (Figure 2b). tainous part of Slovenia (550–650 mm) influenced by In spring, western mountainous Slovenia is still the alpine climate. Southwestern Slovenia is influenced by wettest part of the country (550–650 mm), while the largest submediterranean climate and receives between 250 and part of the country receives more precipitation (250– 350 mm. The largest part of the country receives less than 350 mm) compared to winter. Northeastern Slovenia, influ- 598 Ë Dragan D. Milošević et al. enced by continental climate, receives less than 250 mm country. The largest increase was observed in central (Figure 2c). Slovenia (from 2% to 4% per decade) (Figure 3e). Summer is characterized by a significant increase of precipitation in the eastern part of the country, influenced by continental climate, and reaching its seasonal precip- 3.4 The correlations between atmospheric itation maximum (250–300 mm). The largest part of the circulation patterns and precipitation country receives between 350 and 450 mm, while north- western Slovenia receives between 450 and 550 mm (Fig- In general, correlations between MOi, NAOi and precipi- ure 2d). tation in Slovenia are negative, while WeMOi and precip- In autumn, the seasonal precipitation maximum is ev- itation have positive correlations on annual and seasonal ident in the area of alpine (northwestern Slovenia) and scales (Table 2). This suggests that precipitation in Slove- submediterranean climate (southwestern Slovenia) with nia is decreasing during positive NAO and MO phases, >750 mm and from 450 mm to 550 mm, respectively (Fig- while the positive phase of WeMO results in more precipi- ure 2e). tation in Slovenia. Annual precipitation in Slovenia was significantly in- fluenced by WeMOi at 21 out of 45 stations (significant cor- 3.3 Precipitation trends relations from 0.3 to 0.6), MOi at 17 out of 45 stations (sig- nificant correlations from −0.3 to −0.4) and NAOi at 10 out A non-significant annual precipitation decrease was reg- of 45 stations (significant correlations from −0.3 to −0.4) istered throughout Slovenia. However, statistically signif- (Table 2). The spatial pattern of these relationships showed icant negative trends (from −3% to −6% per decade, i.e. that WeMOi influence is dominant in central and eastern from −28 mm per decade to −127 mm per decade) were Slovenia, while MOi and NAOi influence is dominant in registered at 13 stations out of 45, mainly located in south- western Slovenia with the larger area under the MOi influ- western and northwestern Slovenia (Figure 3a). ence (Figure 4). During winter, non-significant negative trends were The strongest correlations between NAOi, MOi and noted over the majority of the country (36 out of 45 sta- seasonal precipitation in Slovenia are noticed in winter. tions). The largest decrease was noted in northeastern Significant negative correlations (from −0.3 to −0.7) be- (from −4% to −7% per decade) as well as northwestern tween MOi and precipitation are present in the majority of Slovenia and near the Adriatic Sea (from −4% to −6% per the country (43 out of 45 stations) (Table 2). Only stations decade). Only one small part of southern Slovenia is char- located in southeastern Slovenia are not significantly in- acterized by non-significant positive trends (Figure 3b). fluenced by this atmospheric circulation pattern. Similar Spring precipitation decrease was noted in the whole results are obtained between NAOi and precipitation, but country. Non-significant negative trends are registered in with smaller correlation values (from −0.3 to −0.6) and central (from −4% to −6% per decade), western and north- with a smaller covered area (32 out of 45 stations) (Table 2). eastern Slovenia (from −6% to −8% per decade). However, Eastern Slovenia is not covered by significant NAOi influ- a statistically significant decrease was registered at only ence. Significant WeMOi influence is noticed at 31 outof three stations near the Adriatic coast (from −6% to −10% 45 stations with correlation values ranging from 0.3 to 0.6 per decade, i.e. from −24 mm per decade to −49 mm per (Table 2). Central, southeastern Slovenia and the area near decade) (Figure 3c). the Adriatic Sea are not significantly influenced by this cir- A decrease in summer precipitation was noted over a culation (Figure 4). majority of the country (44 out of 45 stations). A statisti- Only WeMOi significantly influences spring precipita- cally significant precipitation decrease was observed at13 tion in the larger part of Slovenia. Compared to this, cor- out of 45 stations mainly in southwestern Slovenia (from relations between MOi, NAOi and precipitation are rather −4% to −10% per decade, i.e. from −20 mm per decade small and non-significant. WeMOi is positively correlated to −46 mm per decade), where influences of submediter- (from 0.3 to 0.5) with precipitation throughout the country ranean and continental climate intertwine (Figure 3d). (40 out of 45 stations) (Table 2), except for small area in the Autumn in Slovenia was characterized by a non- north and northeast (Figure 4). significant precipitation increase over the majority ofthe During summer, the precipitation distribution in the country (35 out of 45 stations), with negative trends (from majority of the country is not significantly influenced by −2% to −4% per decade) noted only in the west of the the investigated atmospheric circulation patterns. It might be that local factors (i.e. orography) shield certain re- Variability of seasonal and annual precipitation in Slovenia Ë 599

Figure 3: Spatial distribution of long-term trends (%/decade) of precipitation amounts (a - annual; b - winter; c - spring; d - summer; e - autumn) in Slovenia during the 1963-2012 period. Values significant at the 95% and 99% level (two-tailed). NS - non-significant. gions from the variability represented by the atmospheric stations, located in the northwestern part of the country modes. As noticed in previous research, at fine geograph- (Figure 4). ical scales the effects of atmospheric circulation are mod- Non-significant correlations were found between MOi, ified by topography, particularly in areas of complex ter- NAOi and autumn precipitation in Slovenia. Compared to rain [37, 38]. Significant influence (from −0.3 to −0.4) of this, WeMOi is significantly correlated (from 0.3 to 0.5) MOi is noticed in eastern Slovenia and WeMOi in north- with precipitation in the majority of the country, except for western Slovenia (from 0.3 to 0.4) (Table 2). Significant small areas in central and northern Slovenia (Table 2) (Fig- NAOi influence− ( 0.3) (Table 2) is registered at only two ure 4). 600 Ë Dragan D. Milošević et al.

Table 2: Correlation coeflcients between annual and seasonal precipitation and atmospheric circulation pattern indices in Slovenia during the 1963-2012 period. Values significant at the 95% (italic) and 99% level (bold) (two-tailed).

Winter Spring Summer Autumn Annual Station NAO MO WeMO NAO MO WeMO NAO MO WeMO NAO MO WeMO NAO MO WeMO BG −0.2 −0.3 0.5 0.0 0.0 0.4 0.3 −0.2 0.0 −0.2 −0.1 0.4 0.0 −0.1 0.2 BLJ −0.5 −0.7 0.2 −0.2 −0.2 0.4 0.0 −0.1 0.4 −0.3 −0.2 0.3 −0.3 −0.3 0.3 BU −0.5 −0.6 0.3 −0.2 0.0 0.5 −0.1 −0.1 0.1 −0.1 −0.1 0.3 −0.2 −0.2 0.3 BZ −0.1 −0.2 0.6 −0.1 0.1 0.5 0.2 −0.2 0.0 −0.2 0.0 0.4 0.0 0.0 0.3 CK −0.4 −0.5 0.4 −0.1 −0.1 0.4 0.0 −0.1 0.3 −0.1 −0.1 0.4 −0.1 −0.2 0.4 CLJ −0.3 −0.4 0.5 0.0 0.1 0.4 0.1 −0.3 −0.1 −0.2 0.0 0.3 −0.1 −0.1 0.2 CV −0.5 −0.6 0.3 −0.3 0.0 0.5 −0.1 −0.1 0.3 −0.2 −0.1 0.3 −0.3 −0.4 0.3 DO −0.4 −0.4 0.4 0.0 0.1 0.3 0.1 −0.3 −0.1 −0.1 −0.1 0.4 −0.1 −0.2 0.2 DV −0.3 −0.4 0.4 0.0 0.0 −0.1 0.1 −0.2 0.2 −0.1 −0.1 0.2 −0.1 −0.1 0.2 FZ −0.4 −0.4 0.4 −0.1 0.0 0.2 0.0 −0.2 −0.1 −0.2 −0.1 0.3 −0.3 −0.3 0.1 GD −0.5 −0.6 0.2 −0.2 −0.1 0.4 −0.2 0.0 0.2 −0.1 −0.1 0.4 −0.3 −0.4 0.3 GG −0.3 −0.5 0.3 0.0 0.1 0.4 0.0 −0.1 0.1 −0.3 −0.1 0.3 −0.1 −0.2 0.2 HB −0.5 −0.5 0.4 −0.1 0.0 0.4 0.0 −0.2 0.1 −0.2 −0.1 0.4 −0.3 −0.2 0.4 JD −0.5 −0.6 0.3 −0.1 0.0 0.5 0.0 −0.1 0.2 −0.1 −0.1 0.3 −0.1 −0.2 0.5 JR −0.4 −0.6 0.2 −0.1 −0.1 0.4 −0.1 −0.1 0.1 −0.1 −0.1 0.3 −0.2 −0.4 0.2 JU −0.5 −0.5 0.3 −0.2 0.0 0.4 −0.1 −0.2 0.2 −0.1 −0.1 0.4 −0.1 −0.3 0.5 KA −0.6 −0.7 0.2 −0.1 0.0 0.1 0.0 −0.1 0.1 −0.2 −0.1 0.0 −0.3 −0.4 0.2 KC −0.2 −0.4 0.4 0.1 0.0 0.3 0.1 −0.3 0.1 −0.2 0.0 0.4 −0.1 −0.2 0.2 KG −0.5 −0.6 0.3 −0.1 0.0 0.5 −0.3 0.1 0.2 −0.2 −0.1 0.3 −0.3 −0.3 0.3 KO −0.4 −0.4 0.4 0.0 0.0 0.4 0.0 −0.3 0.0 −0.2 0.0 0.4 −0.3 −0.1 0.4 KT −0.2 −0.4 0.4 0.2 0.0 0.4 0.0 −0.2 −0.1 −0.1 −0.1 0.3 0.0 −0.2 0.1 KZ −0.5 −0.6 0.3 −0.3 −0.1 0.3 0.0 −0.1 0.2 −0.1 0.0 0.5 −0.2 −0.3 0.5 LD −0.3 −0.4 0.4 0.1 0.1 0.3 0.0 −0.4 0.1 −0.1 0.0 0.4 −0.1 −0.3 0.2 LJB −0.5 −0.5 0.4 −0.1 0.0 0.4 0.0 −0.1 −0.1 −0.3 −0.1 0.3 −0.2 −0.3 0.3 LO −0.5 −0.6 0.2 −0.2 −0.1 0.4 −0.2 −0.1 0.3 −0.2 −0.2 0.4 −0.4 −0.4 0.3 LS −0.3 −0.4 0.4 0.0 0.0 0.4 0.2 −0.3 −0.1 −0.2 −0.1 0.3 0.1 −0.2 0.1 MB −0.2 −0.3 0.4 0.1 0.0 0.4 0.1 −0.3 0.1 −0.2 0.1 0.5 0.2 −0.1 0.3 MI −0.2 −0.4 0.4 0.0 0.1 0.4 0.0 −0.2 0.0 −0.2 0.0 0.3 0.0 −0.2 0.1 MK −0.5 −0.6 0.2 −0.2 0.0 0.5 −0.2 −0.1 0.4 −0.1 −0.1 0.3 −0.3 −0.3 0.4 MO −0.3 −0.4 0.4 −0.1 0.1 0.3 0.0 −0.2 −0.1 −0.1 −0.1 0.4 −0.2 −0.2 0.2 MS −0.2 −0.4 0.4 0.1 0.1 0.3 0.0 −0.3 0.0 −0.2 0.1 0.4 0.0 −0.2 0.1 NM −0.2 −0.3 0.4 0.0 0.0 0.3 0.2 −0.2 −0.2 −0.1 −0.1 0.3 0.1 −0.1 0.2 PD −0.5 −0.6 0.3 −0.1 0.0 0.4 −0.1 −0.1 0.2 −0.1 −0.2 0.3 −0.1 −0.4 0.2 PG −0.5 −0.6 0.2 −0.1 −0.1 0.4 −0.2 −0.2 0.0 −0.1 −0.1 0.3 −0.3 −0.4 0.2 PI −0.5 −0.6 0.3 −0.3 −0.1 0.4 0.0 −0.3 0.1 −0.1 −0.1 0.4 −0.3 −0.4 0.4 PO −0.5 −0.5 0.3 −0.1 0.0 0.4 0.0 0.0 0.4 −0.1 −0.1 0.4 −0.1 −0.3 0.6 PT −0.2 −0.4 0.4 0.0 0.0 0.4 0.2 −0.4 0.1 −0.2 0.1 0.4 0.0 −0.2 0.3 RT −0.5 −0.6 0.3 −0.2 0.0 0.5 −0.3 0.1 0.2 −0.2 −0.1 0.3 −0.3 −0.2 0.3 RU −0.4 −0.5 0.3 −0.2 0.0 0.5 −0.2 −0.1 0.3 −0.2 −0.2 0.3 −0.3 −0.4 0.3 SK −0.3 −0.4 0.5 0.1 0.0 0.4 0.1 −0.3 0.1 −0.2 0.0 0.3 0.0 −0.1 0.2 SL −0.5 −0.6 0.3 −0.2 0.0 0.5 −0.1 −0.1 0.2 −0.1 −0.1 0.3 −0.2 −0.3 0.3 SM −0.4 −0.5 0.4 −0.1 −0.1 0.3 0.0 −0.2 0.1 −0.2 −0.1 0.4 −0.3 −0.4 0.3 SO −0.4 −0.4 0.4 −0.1 0.0 0.3 0.1 −0.2 0.1 −0.1 −0.1 0.4 −0.3 −0.2 0.4 VD −0.3 −0.4 0.4 0.1 0.0 0.4 0.0 −0.3 −0.1 −0.1 0.1 0.4 0.0 −0.1 0.1 ZR −0.4 −0.6 0.2 −0.1 −0.1 0.4 −0.2 −0.1 0.1 −0.2 −0.1 0.3 −0.3 −0.4 0.2

4 Discussion and conclusions ilarities and differences with respect to precipitation fluc- tuations in other areas of the MR. The highest precipitation amounts are registered at The statistical analysis of annual and seasonal data from a the mountains in western Slovenia with a decrease to- network of precipitation stations in Slovenia from 1963 to wards the northeast of the country. This is due to the fact 2012 has allowed for quantitatively characterizing precip- that western Slovenia is exposed to the inflow of moisture itation variability in the study area and for assessing sim- Variability of seasonal and annual precipitation in Slovenia Ë 601

Figure 4: Correlations between annual and seasonal (winter; spring; summer; autumn) precipitation and atmospheric circulation pattern indices in Slovenia during the 1963-2012 period. Values significant at the 95% and 99% level (two-tailed). NS - non-significant. from the Adriatic Sea and to topographically-induced pre- decrease was noticed in spring (from −6% to −10% per cipitation by the Alps and the Dinaric Alps. decade) and summer (from −4% to −10% per decade) and Negative annual and seasonal (except autumn) pre- at an annual timescale (from −3% to −6% per decade) in cipitation trends are observed. A significant precipitation southwestern and western Slovenia. Non-significant de- 602 Ë Dragan D. Milošević et al. creasing trends (up to −7% per decade) during winter and site for winter and autumn seasons compared to the mod- non-significant increasing trends during autumn (up to eled trends. Observed trends also have higher values when 4% per decade) were registered in the majority of the coun- compared to the modeled trends [47]. try. Compared to the study of de Luis et al. [7] that analyzed Correlations between NAOi, MOi and annual and sea- precipitation in Slovenia for the 1950-2007 period, this sonal precipitation in Slovenia are negative. When NAO study obtained higher negative trends during spring and is in its positive phase, low-pressure anomalies over the summer and smaller during winter, while annual trends Icelandic region and throughout the Arctic combine with had the same values. Annual and seasonal trends from our high-pressure anomalies across the subtropical Atlantic to study agree with trends derived from E-OBS gridded obser- produce stronger than average westerlies across the mid- vations [39]. ERA-Interim meteorological reanalysis [40] latitudes. During a positive NAO, conditions are drier over and results from our study showed increasing trend of the MR [48], including Slovenia, as noticed in our study. precipitation during autumn and decreasing trend dur- The negative NAO index phase shows a weak subtropi- ing spring, while they disagree on the winter and summer cal high and a weak Icelandic low. The reduced pressure trends. Trends from NCEP/NCAR R1 meteorological reanal- gradient results in fewer and weaker winter storms cross- ysis [41] and trends from our study disagree during all sea- ing on a more west-east pathway and bringing moist air sons, except for the autumn. into the Mediterranean [49] and increasing precipitation By the end of the 21st century it is expected that pre- amounts into Slovenia. The positive mode of MO is related cipitation in Slovenia will continue to decrease in summer to anticyclonic conditions in the western Mediterranean months (up to 20 %), increase in winter (up to 30%) and and a trough in the east, and with below-average rain- show no significant changes in spring and autumn [42]. fall rates in the entire Mediterranean basin [50], including Furthermore, results from high-resolution climate change Slovenia. In its negative mode, a low pressure region is lo- simulations over the MR showed substantial precipitation cated near the British Isles or north of the Iberian Penin- increases in winter (>25%) and spring (from 10% to 25%) sula while anticyclonic conditions prevail in the Mediter- and a decrease in summer (from −10% to −25%) and a ranean. This situation is related with rainfall events in the small change in autumn precipitation (from −5% to 5%) western part of the Mediterranean basin [19]. Results from in Slovenia by the end of the 21st century [43]. Compared our study indicate more precipitation in Slovenia during to these studies, our results showed significant drying dur- the positive MO phase. NAOi and MOi significantly influ- ing summer and non-significant changes during autumn, ence winter precipitation. In spring and autumn their sig- and this is compatible with model projections for the fu- nificant influence is not registered, while in summer itis ture. Observed winter and spring trends are not compati- limited to a small area. Statistically significant correlations ble with climate model projections. are stronger for MOi than for NAOi. Annual and seasonal precipitation in the MR shows no Correlations between WeMOi and annual and sea- uniform trend. Weak or non-significant trends for precipi- sonal precipitation in Slovenia are positive. The positive tation in the past century have been found at the Mediter- phase of the WeMO corresponds to an anticyclone over the ranean scale [44], in Serbia [6], Israel [5], northwestern Azores and low-pressures in the Liguria Gulf [20], resulting Italy [45], in the Alpine region [46], etc. Seasonal trends in higher precipitation amounts in the larger part of Slove- indicate a slight decrease in winter and spring and an in- nia in all seasons except for summer when its influence is crease in autumn precipitation in Serbia [6]. Lopez-Bustins spatially limited. The WeMO negative phase coincides with et al. [14] noticed a significant decrease of winter rainfall a central European anticyclone located north of Italy and a at the Iberian Peninsula in its western and central areas low-pressure centre in the framework of the Iberian south- throughout the second half of the 20th century, whereas west [20] leading to a precipitation decrease in Slovenia. over the eastern fringe it showed little variation. Obtained NAOi shows a positive and significant (at 95% level) trends in this study together with a projected future pre- trend in the second half of the 20th century [14]. The trend cipitation decrease in the MR [2, 4] that is going to be most of this atmospheric circulation index is consistent with the pronounced in summer [3] could imply that these changes reduction in winter precipitation throughout Slovenia reg- have already started in Slovenia, which could lead to an istered in this paper and in the study of de Luis et al. [7], increased economic and social vulnerability in the coun- and over most of the Iberian Peninsula at the end of 20th try due to reduced water availability in the future. Results century [14]. Also, NAOi displays a strong, negative corre- from this study show drying in the spring and summer lation with winter [45] and spring precipitation in Italy [51] seasons as in the Coupled Model Intercomparison Project and at high altitudes in the Alps [46, 52]. Except with phase 5 (CMIP5) models, but the observed trends are oppo- mean precipitation amounts, NAOi is negatively correlated Variability of seasonal and annual precipitation in Slovenia Ë 603 with the frequency of extreme precipitation days over the References northwestern MR in the period 1961-2000. The correlations are rather small during autumn (October-November) but [1] Lionello P., Abrantes F., Gacic M., Planton S., Trigo R., Ulbrich are quite considerable during the rest of the rainy season U., The climate of the Mediterranean region: research progress (December-January, February-March) [12]. and climate change impacts. Reg. Environ. Change, 2014, 14, MO is strongly linked in winter to NAO [19]. An ob- 1679-1684 served increase in MOi during the second half of the 20th [2] Jacobeit J., Hertig E., Seubert S., Lutz K., Statistical downscal- ing for climate change projections in the Mediterranean region: century [17, 19] led to smaller precipitation amounts south methods and results. Reg. Environ. Change, 2014, 14, 1891- from 50°N [17] which is in accordance with a winter pre- 1906 cipitation decrease in Slovenia when its influence is the [3] Dubrovský M., Hayes M., Duce P.,Trnka M., Svoboda M., Zara P., strongest. Multi-GCM projections of future drought and climate variability WeMOi is significantly reduced in winter throughout indicators for the Mediterranean region. Reg. Environ. Change the second half of the 20th century [20] with WeMO enter- 2014, 14, 1907-1919 [4] IPCC Intergovernmental Panel on Climate Change, The Physical ing an extreme negative phase in the 1990s. This recent Science Basis, Summary for Policymakers (contribution of WG I WeMOi decay leads to a rainfall reduction over the north- to the 4th Assessment Report of the IPCC), Cambridge and New ern fringe of the Iberian Peninsula [14] and torrential rain- York: Cambridge University Press, 2007 fall reduction in the northeastern Iberian Peninsula [21]. A [5] Ziv B., Saaroni H, Pargament R., Harpaz T., Alpert P., Trends in significant increase in sea-level pressure in northern Italy rainfall regime over Israel, 1975–2010, and their relationship to large-scale variability. Reg. Environ. Change, 2014, 14, 1751- has been detected during the twentieth century [53] that 1764 could contribute to the precipitation decrease in Slovenia [6] Luković J., Bajat B., Blagojević D., Kilibarda M., Spatial pattern in all seasons except autumn. In autumn, a large increase of recent rainfall trends in Serbia (1961–2009). Reg. Environ. in cyclone activity was identified in the Gulf of Genoa and Change, 2014 14, 1789-1799 the southern part of the Adriatic Sea that could be respon- [7] de Luis M., Čufar K., Saz M.A., Longares L.A., Ceglar A., Kajfež- sible for the positive trend in autumn precipitation [54– Bogataj L., Trends in seasonal precipitation and temperature in Slovenia during 1951–2007. Reg. Environ. Change, 2014, 14, 56]. 1801-1810 Results from this study contribute to a better under- [8] Hurrell J.W., Decadal trend in the North Atlantic oscillation: re- standing of relationships between atmospheric circulation gional temperature and precipitation. Science, 1995, 269, 676- patterns and precipitation variability in this transitional 679 area. It is shown that the influence of NAO on precipitation [9] Hurrell J.W., Van Loon H., Decadal variations in climate associ- ated with the North Atlantic oscillation. Clim. Chang., 1997, 36, variability over Slovenia is smaller than the effects of the 301-326 atmospheric circulations belonging to the Mediterranean [10] Sušelj K., Bergant K., Mediterranean Oscillation Index. Geo- area (namely WeMO and MO). WeMO appeared as the most phys. Res. Abstr., 2006a, 8, 2145 dominant atmospheric circulation pattern influencing an- [11] Sušelj K., Bergant K., Sredozemski oscilacijski indeks in vpliv na nual and seasonal precipitation variability and distribu- podnebje Slovenije [Mediterranean Oscilation index and its in- tion in the Republic of Slovenia, except for winter when fluence on the climate of Slovenia]. In: Kozmus K, Kuhar M (Ed.), Raziskave s področja geodezije in geofizike: zbornik predavanj MO is the most significant atmospheric circulation pattern. [Researches in geodesy and geophysics: collection of lectures]. Relationships between other weather variables (e.g. tem- Faculty of Civil and Geodetic Engineering, 2006b, Ljubljana (in perature) and atmospheric circulation patterns could be Slovenian) investigated in future papers in order to acquire a more de- [12] Krichak S.O., Breitgand J.S., Gualdi S., Feldstein S.B., tailed picture of climatic change in this country. Teleconnection-extreme precipitation relationships over the Mediterranean region. Theor. Appl. Climatol., 2014, 117, 679-692 Acknowledgement: This research is supported by the [13] Brunetti M., Maugeri M., Nanni T., Atmospheric circulation and project no. 43002 financed by the Ministry of Education, precipitation in Italy for the last 50 years. Int. J. Climatol., 2002, Science and Technological Development of the Republic 22, 1455-1471 of Serbia. [14] Lopez-Bustins J.A., Martin-Vide J., Sanchez-Lorenzo A., Iberia winter rainfall trends based upon changes in teleconnection and circulation patterns. Glob. Planet. Chang., 2008, 63, 171- 176 [15] Conte M., Giuffrida S., Tedesco S., The Mediterranean oscilla- tion: impact on precipitation and hydrology in Italy. In: Proceed- ings of the Conference on Climate and Water, Vol. 1. Publica- tions of Academy of Finland, Helsinki, 1989, 121-137 604 Ë Dragan D. Milošević et al.

[16] Palutikof J.P., Analysis of Mediterranean climate data: mea- Union-General Assembly, Vienna, , 2010, Geophysical sured and modelled. In: Mediterranean Climate-Variability and Research Abstract Vol. 12, EGU2010-5521-1 Trends, Bolle HJ (ed.). Springer-Verlag, Berlin, 2003, 133-153 [36] Moberg A., Alexandersson H., Homogenization of Swedish tem- [17] Piervitali E., Colacino M., Conte M., Signals of climatic change perature data. Part II: homogenized gridded air temperature in the central–western Mediterranean basin. Theor. Appl. Cli- compared with a subset of global gridded air temperature since matol., 1997, 58, 211-219 1861. Int. J. Climatol., 1997, 17, 35-54 [18] Kutiel H., Paz R., Sea level pressure departures in the Mediter- [37] Fernandez J., Sáenz J., Zorita E., Analysis of wintertime atmo- ranean and their relationship with monthly rainfall conditions spheric moisture transport and its variability over southern Eu- in Israel. Theor. Appl. Climatol., 1998, 60, 93-109 rope in the NCEP reanalyses. Clim. Res., 2003, 23, 195-215. [19] Dünkeloh A., Jacobeit J., Circulation dynamics of Mediterranean [38] Bojariu R., Giorgi F., The North Atlantic Oscillation signal in a re- precipitation variability 1948–98. Int. J. Climatol., 2003, 23, gional climate simulation for the European region. Tellus, 2005, 1843-1866 57A(4), 641-653. [20] Martín-Vide J., Lopez-Bustins J.A., The Western Mediterranean [39] Haylock M.R., Hofstra N., Klein Tank A.M.G., Klok E.J., Jones P.D., Oscillation and rainfall in the Iberian Peninsula. Int. J. Climatol., New M., A European daily high-resolution gridded dataset of 2006, 26(11), 1455-1475 surface temperature and precipitation. J. Geophys. Res (Atmo- [21] Martin-Vide J., Sanchez-Lorenzo A., Lopez-Bustins J.A., Cor- spheres), 2008, 113, D20119, doi:10.1029/2008JD10201 dobilla M.J., Garcia-Manuel A., Raso J.M., Torrential Rainfall [40] Dee D.P., Uppala S.M., Simmons A.J., Berrisford P., Poli P., in Northeast of the Iberian Peninsula: Synoptic patterns and Kobayashi S., Andrae U., Balmaseda M.A., Balsamo G., Bauer P., WeMO influence. Advances in Science and Research, 2008, 2, Bechtold P., Beljaars A.C.M., van de Berg L., Bidlot J., Bormann 99-105 N., Delsol C., Dragani R., Fuentes M., Geer A.J., Haimberger L., [22] Orožen Adamič M., About Slovenia. In: Orožen Adamič M (Ed.), Healy S.B., Hersbach H., Hólm E.V., Isaksen L., Kållberg P., Köh- Slovenia: a geographical overview. ZRC SAZU, Ljubljana, 2004, ler M., Matricardi M., McNally A.P., Monge-Sanz B.M., Morcrette 7-9 J.-J., Park B.-K., Peubey C., de Rosnay P., Tavolato C., Thépaut [23] Ogrin D., Prut D. Aplikativna fizična geografija Slovenije [Ap- J.-N., Vitarta F., The ERA-Interim reanalysis: configuration and plicative physical ]. Znantstvena založba performance of the data assimilation system. Q. J. Roy. Meteor. Fikozofske fakultete, Ljubljana, 2009, 13. (in Slovenian) Soc., 2011, 137, 553-597. [24] Perko D., The regionalization of Slovenia. Geografski zbornik, [41] Kalnay E., Kanamitsu M., Kirtler R., Collins W., Deaven D., 1998, 38, 12-57 Gandin L., Iredell M., Saha S., White G., Woollen J., Zhu Y., [25] Ogrin D., Modern climate change in Slovenia. In: Orožen Adamič Chelliah M., Ebisuzaki W., Higgins W., Janowiak J., Mo K.C., Ro- M (Ed.), Slovenia: a geographical overview. ZRC SAZU, Ljubl- pelewski C., Wang J., Leetma A., Reynolds R., Jenne R., Joseph jana, 2004, 45-50 D., The NCEP/NCAR 40-year reanalysis project. Bull. Amer. Me- [26] Alexandersson H., A homogeneity test applied to precipitation teorol. Soc., 1996, 77, 437-471. data. J. Climate, 1986, 6, 661-675 [42] Bergant K., Projections of Climate Change for Slovenia. In: Jurc [27] Khaliq M.N., Ouarda T., On the critical values of the standard M (Ed.), Climate Change: impact on forests and forestry. Studia normal homogeneity test (SNHT). Int. J. Climatol., 2007, 27, 681- forestalia Slovenica, 130, 67-86. 687 [43] Gao X., Pal J.S., Giorgi F., Projected changes in mean and ex- [28] Štěpanek P., AnClim - software for time series analysis. Depart- treme precipitation over the Mediterranean region from a high ment of Geography, Faculty of Natural Sciences, MU, Brno, 1.47 resolution double nested RCM simulation. Geophys Res Lett, MB, 2007 http://www.climahom.eu/AnClim.html 2006, 33, L03706, DOI:10.1029/2005GL024954. [29] Sneyers R., On the statistical analysis of series of observations. [44] Norrant C., Douguedroit A., Monthly and daily precipitation World Meteorological Organization, Technical Note, Genève, trends in the Mediterranean (1950–2000). Theor. Appl. Clima- 1991, 415, 192 tol., 2006, 83, 89-106 [30] Salmi T., Mättä A., Anttila P., Ruoho-Airola T., Amnell T., Detect- [45] Ciccarelli N., von Hardenberg J., Provenzale A., Ronchi C., Vargiu ing trends of annual values of atmospheric pollutants by the A., Pelosini R., Climate variability in north-western Italy during Mann-Kendall test and Sen’s slope estimates. The Excel tem- the second half of the 20th century. Glob. Planet. Chang., 2008, plate application MAKESENS. Finnish Meteorological Institute, 63, 185-195 Helsinki, 2002, 1-35 [46] Beniston M., Mountain and climatic change: an [31] National Oceanic and Atmospheric Association (NOAA) Climate overview of processes focusing on the European Alps. Pure and Prediction Center (CPC) website, 2014 http://www.cpc.ncep. Applied Geophysics, 2005, 162, 1587-1606 noaa.gov/products/precip/CWlink/pna/nao.shtml [47] Kelley C., Ting M., Seager R., Kushnir Y., Mediterranean [32] Climatic Research Unit website, 2014 http://www.cru.uea.ac. precipitation climatology, seasonal cycle, and trend as uk/cru/data/moi/ simulated by CMIP5. Geophys Res Lett, 2012, 39, 21, [33] University of Barcelona website, 2014 http://www.ub.edu/gc/ DOI:10.1029/2012GL053416 English/wemo.htm [48] Visbeck M.H., Hurrell J.W., Polvani L., Cullen H.M., The North At- [34] Savić S., Milovanović B., Lužanin L., Lazić L., Dolinaj D., The vari- lantic Oscillation: past, present, and future. Proc. Natl. Acad. ability of extreme temperatures and their relationship with at- Sci. U.S.A., 2001, 98, 23, 12876-12877. mospheric circulation: the contribution of applying linear and [49] Rousi E., C. Anagnostopoulou C., Tolika K., Maheras P.,Bloutsos quadratic models. Theor. Appl. Climatol., 2015, 121, 591-604 A., ECHAM5/MPI General Circulation Model Simulations of Tele- [35] Savić S., Petrović P., Milovanović B., Homogenisation of mean connection Indices over Europe. In: Helmis CG (Ed.), Advances air temperature data series from Serbia. European Geosciences in Meteorology, Climatology and Atmospheric Physics. Springer Variability of seasonal and annual precipitation in Slovenia Ë 605

Berlin Heidelberg, 709-715. [53] Maugeri M., Brunetti M., Monti F., Nanni T., Sea-level pressure [50] Angulo-Marti?nez M., Santiago Begueri?a S., Do atmospheric variability in the Po plain (1765–2000) from homogenized daily teleconnection patterns influence rainfall erosivity? A study of secular records. Int. J. Climatol., 2004, 24, 437-455 NAO, MO and WeMO in NE Spain, 1955-2006, J. Hydrol., 2012, [54] Bartholy J., Pongracz R., Pattanyus-Abraham M., Analysing the 450- 451, 168-179. genesis, intensity and tracks of western Mediterranean cy- [51] Wibig J., Precipitation in Europe in relation to circulation pat- clones. Theor. Appl. Climatol., 2009a, 96, 133-144 terns at the 500 hPa level. Int. J. Climatol., 1999, 19, 253-269 [55] Bartholy J., Pongracz R., Pattanyus-Abraham M., European cy- [52] Beniston M., Jungo P., Shifts in the distributions of pressure, clone track analysis based on ECMWF ERA-40 data sets. Int. J. temperature and moisture and changes in the typical weather Climatol., 2009b, 26, 1517-1527 patterns in the Alpine region in response to the behavior of the [56] Lionello P.,Zardini, Characteristics of the cyclonic activity in the North Atlantic Oscillation. Theor. Appl. Climatol., 2002, 71, 29- Mediterranean sea during the last four decades of the 20th Cen- 42 tury. Geophys. Res. Abstr., 2003, 5, 8316