Introduction

Foehn wind is a non-periodic phenomenon occurring in most mountains worldwide. Its origin depends on the synoptic situation and terrain relief, and it appears on the lee side as a result of synoptic-scale, cross-barrier flow over the mountain range (Barry and Chorley 2003; American Meteorological Society 2023). Foehn is a very complex atmospheric phenomenon (cf. Hoinka 2007) and the first correct classical theory of its formation was put forward by Julius Hann, an Austrian climatologist (1866, as in Barry 2008). Hann’s theory assumes that foehn is a thermodynamic, descending (katabatic), warm, dry and gusty wind blowing along the leeward mountain slopes. Jansing et al. (2022) refer to the phenomenon as “winds and storms on mountain slopes”. There are several theories of the air descending on the leeward side (after Steinacker 2006; Seibert 2005, 2012), mostly developed in the first half of the twentieth century. Richner and Hächler (2013) postulate that the behaviour of air masses after crossing a mountain ridge is among the least understood mechanisms in flow dynamics. Hann (1866, as in Barry 2008) has postulated that conditions conducive to the formation of a foehn include a high pressure system on one side of a mountain chain, and a low pressure centre on the other side. The pressure gradient on either side of the mountain chain forces air masses over the mountains to flow from high pressure to low pressure, taking into account the Coriolis force. At the peaks of a mountain chain, wind speed increases which is related to the narrowing of the airflow section (Kożuchowski 2012). On the leeward side, the air flows katabatically, according to the slope of the terrain, and it warms according to the dry adiabatic gradient; the spontaneous heating and drying of air masses is referred to as the foehn effect (Kaczorowska 1977; Trepińska 2002; Barry and Chorley 2003). According to Hoinka (1985), an increase in air temperature can be recorded even 100 km from the mountain barrier. As the distance from the barrier grows, foehn wind loses its speed and gustiness and can only be identified based on the so-called foehn effect: an increase in temperature and a decrease in air humidity (Hoinka 1985). Foehn occurrence in the Polish Carpathians contributes to an increase in the mean annual temperature by approximately 1 °C and a decrease in relative humidity by approximately 10% (Ustrnul 1992a). Sometimes, the air temperature can grow significantly, with increases by 30 °C reported in the literature on the subject (Seibert 1990; Trepińska 2002). Descending dry air masses can cause the dispersion of clouds and create a rain shadow (Barry and Chorley 2003). As far as the warming mechanisms on the leeward side are concerned, the dynamic and thermodynamic warming mechanisms are among the best known (Barry 2008; Richner and Hächler 2013). Elvidge and Renfrew (2016) have been the first to quantify the contribution of the most important mechanisms leading to foehn warming, such as the isentropic adiabatic process during descending air motion, the latent heat exchange mechanism, and the mechanism of turbulent mixing of air, to name a few. According to them, each of the above-mentioned processes leading to an increase in temperature on the leeward side can be dominant, depending on the airflow dynamics.

The occurrence of foehn winds is of biometeorological importance and can influence changes in air pollutant concentrations on the leeward side of a slope (cf. Weber and Prévôt 2002; Solomos et al. 2018). There are papers in literature on the subject that document both decreases (Furger et al. 2005; Druet and Wiśniewski 2021) and increases in pollutant concentrations and deterioration of air quality during foehn winds (Nkemdirim and Leggat 1978; Natale et al. 1999; Seibert et al. 2000; Mintz et al. 2003; Gunia et al. 2008; Li et al. 2002). Gaffin (2007) has identified the typical characteristics and synoptic conditions of a foehn that caused large temperature changes over the southern Appalachians. Typically, foehn on the western side of the Appalachians occurred during the south-easterly circulation and developed in the foreground of a low pressure system located over the Mississippi Valley. In contrast, foehns on the eastern side of the Appalachians were mainly north-westerly in direction, and associated with the passage of a shallow cold front. Speirs et al. (2010) have concluded that foehn occurrences in the McMurdo Dry Valleys in Antarctica are caused by strong pressure gradients over mountain ranges associated with synoptic-scale cyclones located off Marie Byrd Land.

Stachlewski (1974) has investigated the circulation origin of foehn occurrences in the Polish Tatra Mountains and their foreland on the basis of the Konček and Rein’s (1971) calendar of atmospheric circulation types in Central Europe. The following circulation types were particularly conducive to foehn occurrence: southern anticyclonic, western cyclonic, south-western cyclonic, low pressure trough over Central Europe and a central cyclone. In an analysis of two severe cases of the halny wind in the Tatra Mountains, Śliwińska and Ciaranek (2015) have pointed out that synoptic conditions were affected by a quasi-stationary high-pressure ridge that extended to the south-east of Poland and a low pressure located over north-western Poland.

The aim of the study was to determine the climate-related regularities with regard to the potential occurrence of the halny wind on the Polish side of the Tatra Mountains, represented by the high-mountain station on Kasprowy Wierch, and to establish typical pressure field systems and synoptic conditions over Europe during days with halny.

Study area, materials and methods

The research area of the Polish Tatra Mountains is represented by the meteorological station of the Institute of Meteorology and Water Management-National Research Institute (IMGW-PIB) located on Kasprowy Wierch at 1990 m a.s.l. (49°14′ N 19°59′ E) (height and position after danepubliczne.imgw.pl). The Tatra Mountains range is a part of the Carpathians, falling in Poland and Slovakia (Fig. 1). The Tatras are characterised by a high mountainous relief with steep slopes and high elevations. They are surrounded by long and extensive valleys, especially on the southern side which means that air masses moving northwards encounter a significant altitude barrier, initiating the formation of the halny wind on the Polish side of the Tatras. Their considerable altitude contributes to significant changes in the speed and direction of the flowing air masses (Morawska 1968).

Fig. 1
figure 1

Location of the study area (down–left map); morphology of the Tatra Mountains with the location of the IMGW-PIB station on Kasprowy Wierch (upper map); vertical cross-section along the 20° E meridian showing the terrain relief (down–right profile) (according to < mapsforeurope.org > and < ec.europa.eu >)

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In the study, hourly data on wind speed and direction from Kasprowy Wierch for 1995–2020 were used (danepubliczne.imgw.pl). Applying the criterion suggested by Ustrnul (1992b), the potential conditions for the occurrence of halny were considered to be the flow of air masses across the main ridge of the Tatra Mountains at the location represented by Kasprowy Wierch with a wind speed ≥ 10 m/s from the southern sector between 140 and 220° (SE–SW). A persistence criterion of 6 h without interruption was taken into account to exclude short-lived wind speed increases which may be caused by local factors or the passage of a front. The adopted method only allows the identification of potential conditions for the occurrence of foehn wind, as it does not ensure that all occurrences are taken into account due to the adopted high threshold for wind speed and duration. On the other hand, there is a possibility of overestimating the number of occurrences or hours of the phenomenon. Therefore, it should be underlined, that cases of potential occurrence of halny were analysed in this study, and not the real cases of halny.

The climate analysis of the occurrence of the potential halny wind was carried out based on the number of events and duration thereof, using basic statistics. Wind frequencies from different directions were determined using a 16-sector wind rose.

To recognize synoptic conditions favourable for the occurrence of the halny wind, reanalysis data were used, including daily mean sea level pressure (SLP), and air temperature at 850 hPa geopotential height (T850). Data for the area 30–75° N latitude/15° W–45° E longitude, resolution 2.5° × 2.5°, were derived from the NCEP-DOE (National Centers for Environmental Prediction-Department of Energy) Reanalysis 2 (Kanamitsu et al. 2002). Composite mean and anomaly maps of SLP and anomaly maps of T850 were constructed to show the atmospheric conditions of the halny events. The anomalies were computed separately for each grid point and each day of the year as deviations from the 1995 to 2020 means. Furthermore, to detect the variability within the SLP fields in the days of foehn wind occurring in the Polish Tatras, Ward’s (1963) minimum variance method was applied. Ward’s method is a hierarchical clustering technique frequently used for climatic classifications (Kalkstein et al. 1987). In this study, the clustered objects were the days with the halny wind, and the clustering was based on the normalized daily SLP data. Composite and anomaly maps of SLP and T850 were constructed for each cluster, showing different pressure patterns favourable for the halny wind.

Results

Climatology of potential foehn occurrence

The halny wind is an annually variable and random weather element, which is why no statistically significant general trend in its occurrence has been recognised over the studied multiannual period. In 1995–2020, a total of 1,124 events were recorded with potential conditions of halny occurrence, i.e., with the occurrence on Kasprowy Wierch of winds from the southern sector with the assumed speed (≥ 10 m/s) and duration (≥ 6 h). On average, 43 such events occurred per year and lasted a total of approximately 24 days, with the biggest number of events recorded in 2010 (67), and the smallest (26) in 2015 (difference of 41) (Fig. 2a, b). The coefficient of variation for the annual number of halny events is 23%, indicating relatively low multi-year variability.

Fig. 2
figure 2

Multiannual (a) and seasonal (c) variation in the number of cases (–) and total duration (h) of halny wind in the years 1995–2020 (b, d)

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Halny occurrences are more frequent in the cold half-year (October to March, 73% of all cases). While on average there were 4 halny winds per month, a clear seasonality in the occurrence of the phenomenon was observed in the annual course (Fig. 2c). Most episodes were recorded in the autumn (October, November) and winter months (December, January, February), with a maximum in November (7 cases on average, lasting a total of 110 h—Fig. 2d). In the summer, halny occurs least frequently with a minimum frequency in July and June (one case lasting 12–13 h on average).

The average duration of a halny wind episode over the multiannual period studied amounted to approximately 13 h (median of 10 h). As the duration of a halny wind episode increases, the number of cases decreases, as shown in the density plot (Fig. 3a). A halny wind lasting more than two days (> 24 h) was observed very rarely, with the longest occurrence of potential halny wind conditions lasting 79 h (03 November 2014). Short-lived episodes, lasting between 6 and 8 h, were observed most frequently (approximately 37% in total). The variation coefficient for the duration of the halny wind is 66%, indicating a highly variable duration of foehn wind in the Tatras. Annually, the duration is clearly seasonal (Fig. 3b). Long-term foehns lasting more than 48 h occurred in the cold season (October–January, March). In the warm season (May, June, August), no halny wind blew for more than 24 h.

Fig. 3
figure 3

a Density plot of the duration of halny wind (h); b Scatter plot of the duration of halny wind (h) on an annual basis in the years 1995–2020

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The occurrence of halny winds is characterised by a distinct diurnal cycle, especially in the warm half of the year (Fig. 4). Foehn episodes occurred more frequently during night hours, and usually started in the afternoon and evening (3:00–10:00 p.m.) with a maximum at 7:00 p.m. (83 cases). They ended mostly in the night, morning and before noon.

Fig. 4
figure 4

Daily (UTC hours) and seasonal variability in the number of recorded occurrences of halny wind (based on data from years 1995 to 2020)

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Anemometric conditions on Kasprowy Wierch

As the wind on Kasprowy Wierch was a criterion for identifying conditions conducive to the occurrence of the phenomenon in question, a frequency/speed analysis for individual wind directions was carried out on the basis of archived results of hourly measurements. The wind rose for Kasprowy Wierch, plotted for years 1995–2020, shows the average annual frequency of wind incidence in the speed ranges from each direction (Fig. 5a). On average, there is a clear predominance of NNE (almost 14%) and SSW (almost 12%) winds per year while winds from E, ESE, SE and SSE are least frequent (less than 4%).

Fig. 5
figure 5

a Mean annual direction and speed wind rose (%, m/s); b Wind speed histogram (m/s) for hours with the halny wind; c Direction and speed wind rose for hours with halny wind (%, m/s)

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The average wind speed on Kasprowy Wierch was 6.4 m/s, and the proportion of atmospheric calm episodes was only about 0.9%. The most frequent wind speeds were in the range of 2 m/s to 8 m/s. The share of wind speeds above 17 m/s was negligible, and the maximum recorded speed reached 32 m/s (~ 150 km/h). The coefficient of variation of wind speed was 60% (strong variability). Winds with significant speed (> 11 m/s) most often blew from the SSW, S and SW directions, while weak (0.3–4.9 m/s) and moderate (5.0–7.9 m/s) winds were most often from the NNE, N or NE directions.

During the selected hours with recorded foehn, the average wind speed on Kasprowy Wierch amounted to 13.5 m/s, with air masses arriving from the direction of 192° on average (Fig. 5b, c). The prevailing direction of the inflow of air masses during halny episodes was SSW (above 42%), followed by S (above 36%) (Fig. 5c) which may be attributed to wind channelling in the vast and deep Silent Liptovská Valley oriented SSW-NNE (Fig. 1). The other directions in the southern sector (SE-SSE-SW) were of lesser significance (below 20% in total) (the smallest share from the SSE direction), which may be due to circulation conditions and the barrier of the highest Tatra peaks encountered by air masses coming from these directions (Fig. 1). The most frequently occurring was the halny wind with a speed of 10–13 m/s; the number of cases of halny decreased as the wind speed increased (Fig. 5b). Winds with speeds above 11 m/s blew most often from the SSW and S direction. In the analysed multiannual period, the maximum speed of halny of 30 m/s (108 km/h) was recorded on 28 December 2003.

During the seasons, the directions of air masses inflow during the halny wind have a pattern resembling that during the average annual conditions. In the cold season (autumn, winter), higher wind speeds are observed much more frequently than in summer. Foehn winds with extremely high velocity were most frequent in winter. The highest average foehn speeds occurred in December (14.2 m/s), and the lowest in August (11.9 m/s).

Synoptic conditions of potential foehn occurrence

The multiannual mean distribution of SLP over the Euro-Atlantic sector is characterised by the highest pressure in the south-west (> 1018 hPa), and a latitudinal ridge of elevated pressure over southern and Central Europe (1015–1017 hPa). The pressure decreases towards the north to < 1008 hPa in the north-west (Fig. 6). The SLP is characterised by a slight gradient, with the isobars in Central Europe having a latitudinal course, while in northern Europe the isobars deviate in a north-easterly direction. This arrangement of the SLP results in air masses mainly arriving over Europe from a westerly direction.

Fig. 6
figure 6

Mean SLP (hPa) in the years 1995–2020 (the area of the Tatra Mountains is marked with a red rectangle)

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In order to recognise the weather conditions favourable to the occurrence of the halny wind in the Tatras, composite maps of the SLP means and SLP anomalies over the European sector were constructed for days with potentially occurring halny (Fig. 7a, b). The pressure field shown differs significantly from the multiannual average conditions (cf. Figures 6 and 7a). The atmospheric circulation for days with the halny wind is affected by two pressure systems, causing air masses to flow from the south-west to the north-east. A low-pressure system forms over north-western Europe with its centre over the Shetland Islands (< 1001 hPa); this is also an area of negative SLP anomalies (down to − 10 hPa, Fig. 7b). At the same time, there is an above-average pressure (1018–1022 hPa) over south-eastern Europe, an area of positive SLP anomalies (+ 2 hPa, Fig. 7b). Air masses generally move parallel to the isobars (which over central-eastern Europe have an SSW-NNE course), indicating a circulation from the SSW direction in the Tatra region (Fig. 7a), in accordance with the prevailing wind direction on Kasprowy Wierch during the halny wind (Fig. 5c). The horizontal SLP gradient over Europe for days with halny above the multiannual average may indicate a stronger flow of air masses from the southern sector.

Fig. 7
figure 7

a Mean SLP (hPa); b SLP anomalies (hPa); c T850 anomalies (°C) for days with halny in the Tatras in the years 1995–2020 (the area of the Tatra Mountains is marked with a red rectangle)

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A map of air temperature anomalies in the low troposphere (T850) was plotted (Fig. 7c) to determine the thermal properties of the masses over Europe during the days with halny. Positive T850 anomalies over central and southern Europe with the centre close to the Tatras (> 3 °C) occurred during the days with halny. Negative T850 anomalies occurred over the western part of the continent with the centre over the Celtic Sea (< − 2 °C). The above air temperature values indicate the advection of warm air masses from the south over central and eastern Europe.

The location and intensity of centres of atmospheric impact during the occurrence of the halny wind may vary, therefore, an attempt was made to distinguish different types of circulation favouring intense southern circulation in the Tatras. Ward’s method was used to distinguish the three most significant clusters, i.e., types of circulation during days with halny over the analysed multiannual period (Fig. 8, column a).

Fig. 8
figure 8

Three circulation types (T1, T2, T3) conducive to the occurrence of halny wind in the Tatra Mountains in the years 1995–2020; columns: a mean SLP (hPa); b SLP anomalies (hPa); c T850 anomalies (°C) (the area of the Tatra Mountains is marked with a red rectangle)

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Type 1, which occurred most frequently (580 days), is characterised by the presence of a deep and extensive low pressure system with its centre over northern Europe and an area of elevated SLP in the southern part of the continent. The highest SLP values were recorded over the area east of the Black Sea and south-west of Portugal (> 1021 hPa), and the lowest over Norway (< 999 hPa). The counter-clockwise circulation around an extensive low causes a south-westerly air flow in southern Poland (Fig. 8, T1_a). Type 1 is characterised by the smallest negative and positive SLP anomalies of the three designated circulation types (T1_b in Fig. 8). It is dominated by a widespread area of negative anomalies (with a centre over northern Denmark <  − 12 hPa) which covers the whole of Europe except for its peripheral south-eastern areas, where small positive anomalies (> 1 hPa) occur.

Types 2 (occurred in 532 days) and 3 (occurred in 366 days) are characterised by fairly similar circulation conditions, with a bipolar pattern of pressure centres along the latitudinal line (Fig. 8, T2_a and T3_a). However, in Type 2, the cyclone is shallower (1001 hPa) and shifted southwards (over Ireland); it is an area of negative SLP anomalies (< − 13 hPa) (T2_b in Fig. 8). The area of elevated pressure is vast and extends east of Poland; in eastern Europe, the SLP reaches 1023 hPa. An area of elevated pressure and positive SLP anomalies (> 8 hPa) extends over northern Europe where the cyclonic systems typical of this latitude disappear, giving way to a high-pressure ridge. In Type 2, the SLP pattern differs dramatically from the multiannual average; in central Europe the isobars run almost along the meridians. This SLP pattern results in a southerly air flow. In Type 3, a deep cyclonic centre (< 898 hPa) extends over the North Atlantic with a centre over the Faroe Islands (T3_a in Fig. 8). This is an area of significant negative SLP anomalies (< − 16 hPa) (T3_b in Fig. 8). The area over north-western Europe is characterised by large SLP gradients. In south-eastern Europe, elevated pressure (1020–1025 hPa) is observed, with positive SLP anomalies (> 5 hPa) with a centre over eastern Ukraine. This bipolar SLP system results in a strong south-westerly flow over the Tatras. Type 3 is characterised by the greatest horizontal pressure gradients among the three circulation types. Therefore, the flow of air masses is strongest in this circulation type. All of the three circulation types share the occurrence of deeper negative anomalies than positive anomalies, indicating the major role of the cyclonic circulation in sha** the anemometric conditions during the occurrence of the halny wind.

The spatial distributions of T850 anomalies for the three circulation types vary only slightly, the common feature being the occurrence of positive T850 anomalies distributed over central and eastern Europe along the meridional flow of air masses (Fig. 8, column c). The largest temperature anomalies over a wide area up to northern Europe occur in Type 3; they reach the highest values (> 4 °C) over the Tatras (Fig. 8, T3_c). In all the three circulation types, negative T850 anomalies occur in western Europe (up to < − 3.2 °C in type 2).

Conclusions and discussion

In the analysed multiannual period, there has been no statistically significant trend in changes to the frequency and duration of the halny wind on Kasprowy Wierch. Łapińska and Bednorz (2013) have noted a markedly decreasing frequency of halny on Kasprowy Wierch between 1971 and 2009. On average, 43 halny occurrences were recorded per year between 1995 and 2020, whereas using similar criteria for determining halny, Łapińska and Bednorz (2013) have identified an average of 32 foehn cases per year between 1971 and 2009. This could suggest an increase in their number over a longer time window. However, the difference in number of halny episodes may be due to the different time resolution of the source data. In Łapińska and Bednorz (2013) 3 h step was taken, while hourly data were used in this study. Besides, Łapińska and Bednorz (2013) used wind direction data rounded to the nearest 10 degrees, while in this document, no rounding to tenths was proceeded, which could also affect the number of the potential foehn situations. Ustrnul (1992b) has found that on average, there are 105 days per year with a potential foehn, i.e., when the average wind speed on Kasprowy Wierch exceeds 10 m/s. In Zakopane, 95 days with classic foehn are recorded per year (Ustrnul 1990, as in Niedźwiedź 1992). The reported average number of days with potential foehn is significantly higher than the average annual number of events identified in this study, as night-time halny was confined to two days. Moreover, sometimes the duration of foehn exceeds 24 h. The number and trends of changes in the frequency of foehn events in other mountain regions vary, e.g., in a long-term (1864–2008) analysis of foehn in Altdorf (Switzerland), Gutermann et al. (2012) have recorded an average of 60 foehn events per year and, while they have found no significant trend in occurrence, they detected its inter-decadal stability. Stoev and Guerova (2020) have observed a trend of a decreasing number of days with foehn after 2004 in Sofia (Bulgaria) between 1974 and 2014, probably caused by changes in the trajectory of Mediterranean cyclones over Hungary. Foehn on the southern side of the Alps in Switzerland occurs 23 days per year and is clearly of seasonal nature with a maximum in winter (Weber and Prévôt 2002).

In the Polish Tatra Mountains, as in other mountain ranges, the occurrence of foehn events is distinctly seasonal. The seasonal variability of this phenomenon is controlled by the meteorological situation depending on the season. In the cool season, higher wind speeds are observed more often than in the warmer season. According to Kożuchowski (2011), this should be attributed to a large pressure gradient in low pressure areas rapidly moving over Poland in winter, while Stachlewski (1974) explains it by an increase in atmospheric circulation activity in the cool season. The strongest wind recorded on Kasprowy Wierch since the station’s existence was halny on 6 May 1968, with a speed of 80 m/s (288 km/h) (Niedźwiedź et al. 1985). Halny, a high-velocity wind, is by far the most frequent in the cold season of autumn and winter. The maximum frequency of halny occurrence was recorded in November, with an average of 7 cases per month. According to Łapińska and Bednorz (2013), the maximum frequency falls in October. Niedźwiedź (1992) has found that foehn in the Tatra Mountains most often occurs between October and May. For the years 1956–1965, Stachlewski (1974) has recorded the highest relative frequency of potential foehn on Kasprowy Wierch in the autumn–winter period with a maximum in December at favourable circulation types, and the lowest frequency in May. He has also found that the reduction in the frequency of foehn events in the cold season was influenced by thermal inversions on the northern side of the Tatra Mountains. Between 1995 and 2020, halny winds were least frequent in June and July (one event per month on average). A different seasonal pattern of foehn occurrence is observed in the Alps, where northern foehn is more frequent in winter and spring than in summer and autumn (Weber and Prévôt 2002; Ambrosetti et al. 2005). In Switzerland, the largest number of foehn cases (more than 6 days) occur in the spring, between March and May, and the smallest (less than 2 days) in July and August (Gutermann et al. 2012). In Bulgaria, foehn winds were most frequent between February and April, and least frequent between June and September (Stoev and Guerova 2020). In the Appalachians, western and eastern foehn events were most often recorded between late autumn and early winter, most likely influenced by favourable synoptic situations, and the vertical stability profile of the atmosphere during the cooler season (Gaffin 2007). In Japan, southern foehn winds most often occurred in the spring, with a maximum in April, during which period extra-tropical cyclones and anticyclones often pass over the island (Kusaka et al. 2021).

In the present study, it was found that halny occurs in a specific diurnal cycle and most frequently, starts in the afternoon, evening and early night, and least frequently between 10 a.m. and 2 p.m. In the warmer season, a higher frequency of night-time halny is observed, than in the daytime. In Japan, southern foehn occurs more frequently at night and less frequently during the day. This is due to the removal of the nocturnal stable layer and the development of a local daytime pressure gradient on the lee side (Kusaka et al. 2021). Richner and Gutermann (2007) point out that the variability in the occurrence of foehn at different times of day has not yet been fully explained due to the interaction of foehn with local wind systems.

During the occurrence of the halny wind in the Polish Tatra Mountains, the air pressure systems deviated from the climatic standard and were characterised by larger pressure gradients and bipolar systems of pressure centres. Foehns in the Tatra Mountains occurred during low air pressure over north-western Europe and higher-than-normal air pressure in south-eastern Europe. This SLP field and a near-southern isobar pattern resulted in an inhibition of the westerly circulation and an influx of air masses mainly from the south and south-west.

A diversification in the location and intensity of cyclonal and anti-cyclonal centres has been shown, with the occurrence of strong negative pressure anomalies over western and north-western Europe being the common feature. Type 1 can be classified as a south-western cyclonic circulation type (SWc), while type 3 can be classified as a south-western anticyclonic type (SWa). Type 2 could be classified as a southern cyclonic pattern. (Sc). In Stachlewski’s research (1974), the occurrence of foehns was particularly favored by circulation types such as: southern anti-cyclonal, western cyclonic, south-western cyclonic, low pressure trough over Central Europe and a central cyclone. The obtained results are related to those in this work. Type 1 can be identified with the south-western cyclonic and Stachlewski (1974) mentioned that, among others, south-western anti-cyclonal (Type 2 in this paper) appears less often, but has a high probability of occurrence of foehn. Type 1 is characterised by the smallest negative and positive SLP anomalies and an extensive low pressure system centred over northern Europe and an area of increased SLP in the southern part of the continent. In type 2, the low pressure centre is moved over western Europe, and the high pressure centre is moved over the eastern part. Type 3 is characterized by the largest horizontal pressure gradients, the low pressure centre is located over Shetland and the high pressure centre is located over south-eastern Europe. Diversification in the location and intensity of baric centres influences the direction of mass air inflow. In types 1 and 3, the air masses come from the south-west over the Tatra Mountains. The bipolar barometric system on the east-west line in the type 2 causes air masses to flow from the south. Śliwińska and Ciaranek (2015) have noted that weather conditions during two strong foehn winds in the Tatras were affected by a quasi-stationary high-pressure ridge that extended to the south-east of Poland and a low air pressure area in north-western Poland. During high pressure in the Tatra Mountains, air masses over central Europe are warm, as indicated by positive air temperature anomalies in the low troposphere. Gaffin (2007) has reported that a relatively warm air mass at an isobaric height of 850 hPa was probably the source area of the Appalachian foehn.