of Geology, Geography and Geoecology

. The work analyzes the dynamics and regime of atmospheric precipitation in the cross-border region of Poland-Belarus-Ukraine during the period 2010-2018. This time period was chosen, in particular, due to the need to find the prerequisites for the strong shallowing of lake complexes and the depletion of groundwater in the Polish region in 2019, which caused significant social and scientific resonance. The source data for the statistical part of the work were archival information from 17 weather stations in the specified region for this period. The main results of the study: 1) the dynamics of the average monthly precipitation amounts for each meteorological station were calculated and analyzed (Lutsk, Svityaz, Manevychi, Kovel, Liubeshiv, Volodymyr, Rivne, Dubno, Sarny, Brody, Rava-Ruska, Kamianka-Buzka, Pinsk, Pruzhany, Terespol, Wlodawa, Zamosc), the average amounts of precipitation that fell during the warm season of the year (IV-X months) and the cold season of the year (XI-III months), average annual precipitation amounts and precipitation amounts for the entire period, which was investigated (2010-2018). All calculated indicators were compared with the data of the climatic norm of 1961-1990). The annual number of days with precipitation, the warm and cold periods of the year, and the average values of this indicator were also determined. Based on the results of the statistical analysis, charts, cartograms, and several diagrams were developed that visually represent the peculiarities of the dynamics of atmospheric precipitation in the studied region during the analyzed period (2010-2018). 2) on the basis of the calculated indicators, maps of the geographical distribution of precipitation amounts on the territory of the cross-border region Poland-Belarus-Ukraine during the studied period (annual amounts, cold and warm season amounts) were constructed. When comparing them with maps of the period of the 20 th century. Changes in the geography of distribution and trends of modern growth of precipitation amounts in the study region were revealed. After the analysis, a number of conclusions and generalizations were made: 1. During the period 2010-2018 in the territory of the cross-border region Poland-Belarus-Ukraine, the average annual amounts of precipitation increased by 20-45 mm compared to the climatic standard, while the average annual number of days with precipitation decreased by 25-30%. 2. Annual amounts of precipitation exceeded 600 mm at almost all (16 out of 17) meteorological stations whose data were analyzed. 3. The distribution of days with atmospheric precipitation during the seasons of the year has changed. The ratio between the amounts of precipitation that fell in the warm and cold periods of the year changed from 75/25 to 60/40 on average. In general, in the studied region, there are trends towards a slight increase in annual precipitation amounts, a redistribution of precipitation amounts in liquid and solid state in favor of rains, and a reduction in the total number of days with precipitation during the year and a more even distribution of them during the warm and cold seasons, compared to the climatic norm.


Introduction
Regional fluctuations in the values of climatic indicators, which have appeared on the territory of Ukraine in recent decades, are associated with the processes of global changes in the Earth's climate. Climatic changes affect all areas of human activity, because the functioning of the agricultural complex, transport, construction complex, communal and household economy, and finally, people's daily life are significantly dependent on weather conditions. Regional manifestations of such changes in the typical course of climatic processes often differ significantly, and the study of these differences is an important and urgent task. In particular, this concerns the study of the dynamics and regime of atmospheric precipitation. Precipitation, its amount and dynamics during the year, and precipitation seasons are one of the determining factors that shape the hydrothermal regime of the territory. The impact of precipitation on the wetting regime is decisive, and this, in turn, affects changes in the water content of the main surface and underground water bodies of the land, on processes of a geological and geomorphological nature (water erosion), on the development and functioning of biocenoses and ecosystems.
Comprehensive studies of natural processes in the cross-border region Poland-Belarus-Ukraine (PL-BY-UA transborder region) actively began after the implementation of the cross-border cooperation program Poland -Belarus -Ukraine, within the framework of which economic, research and communication activities were carried out in 2014-2020, aimed at strengthening the interaction and cooperation of territorial communities, scientists, employees, state and public structures of the three countries in the specified region. The implementation of this Program gave impetus to many scientific investigations, and also showed the importance of a comprehensive study of the natural landscape complexes of this cross-border region. The region, located in the Polissya (Polesia, Polesie) natural zone, was traditionally characterized by sufficient, and in some places, excessive moistening of natural complexes. Thanks to this hydrothermal regime, large wetland systems were formed, which were significantly transformed in the middle of the 20 th century in the process of large-scale drainage and reclamation works. Nowadays, the negative impact of these reclamations on the ecological systems of the region is actively discussed in the scientific literature (Tarasiuk & Hanushchak, 2017), and the need and possibility of renaturalization of wetland complexes in the areas where drainage reclamation systems were created.
During the last decades, regional climatic changes in connection with the prolonged consequences of drainage reclamations cause several local ecological problems, which may eventually spread to large areas and lead to negative transformations of the natural complexes of Polissya. Among these problems are: 1) dust storms and dispersal of drained peat-swamp soils; 2) a decrease in the level of groundwater and aquifers (water «leaves» from wells in Polish villages, this is a trend of recent decades); 3) local shallowing, overgrowth and waterlogging of lakes; 4) large-scale forest fires in the warm period of the year; 5) fires and burning of peatlands; 6) catastrophic spread of tree pests (top pine bark beetle and others); 7) suppression of vegetation in biocenoses that require conditions of sufficient moisture, especially wetland complexes, etc.
All the mentioned problems are to one degree or another related to the regime of atmospheric precipitation, which determined the relevance of this study. The purpose of its implementation was the analysis of modern changes and trends in the dynamics of the amount and regime of atmospheric precipitation in the cross-border region Poland-Belarus-Ukraine, carried out based on the data of 17 meteorological stations of Ukraine, the Republic of Poland, and the Republic of Belarus, located within this region.

Review of previous studies
The regime of atmospheric precipitation and moistening of the study area was studied in sufficient detail, starting with the first scientific explorations of the natural conditions of the Polish region, carried out in the late 19 th and early 20 th centuries by scientists I.I. Zhilinskyi, P.A. Tutkovskyi, V.D. Laskarev, later by the Polish researchers S. Lenzewicz (Lenzewicz, 1931), E. Ryule, S. Kulchytskyi, and later -in the works of a number of climatologists, hydrologists, ecologists both in Ukraine and in neighboring Poland and Belarus.
Precipitation regime in the region during the 20th century.
During the year, precipitation was unevenly distributed. Approximately 70-75% of them fell in the warm period of the year (April-October), and only 30-25% -in the cold period (Gerenchuk, 1975). During the warm season, there were an average of 60-65 days with precipitation exceeding 1 mm per day, 25-28 of which were the days with precipitation exceeding 5 mm. During the year, 160-180 days with precipitation were observed. In winter, these days are more than in summer, but the intensity of winter precipitation was insignificant. In summer, precipitation is often accompanied by thunderstorms and downpours. On average, 81% of liquid, 10% of solid, and 9% of mixed precipitation fell during the year.
Two or three rainless periods were observed in the region in the warm half of the year, with a total duration of up to 10 days. Rainless periods, the duration of which would be more than 10 days, were generally a rather rare phenomenon that could be observed not every year, but once every 5-10 years. Snow cover in the cold season, which appeared at the end of the second decade of November -beginning of December, grew unevenly, frequent thaws prevented its formation. The duration of permanent snow cover varied from the north of the region to the south from 120-130 to 85-95 days. The destruction of the snow cover occurred at the end of February -in the first decade of March, and its complete disappearance -in the 3 rd decade of March. However, in some winters, snowfalls were observed as early as April (Gerenchuk, 1975;Babichenko & Zuzuk, 1988;Melnik, Buyakov, Chernyshev, 2019).
In the distribution of precipitation during the year, the lowest amount occurred in the winter months and March (25-40 mm), and the maximum -in the summer (July). The largest amount of precipitation exceeded the average monthly indicators by 2-3 times. Autumn is an intermediate season when 80-220 mm fell. The minimum amount of precipitation was 270 mm per year. In some months, the amount of precipitation amounted to 1-2 mm or was close to 0. Sometimes in summer day time, up to 150% of the monthly precipitation rate fell (Chemerys, 2000;Gerenchuk, 1975).

Precipitation regime in the region at the beginning of the 21 st century.
Climatic changes at the end of the 20 th century and their regional manifestations for the studied region were analyzed in the works of N.A. Tarasyuk (Barabash, Korzh, Tatarshuk, 2004;Barabash et al., 2009;Tarasyuk & Hanushchak, 2017;Osadchyy, 2012;Martazinova & Shchehlov, 2018;Osuch et al., 2016;Fedoniuk & Kostiv, 2018;Fesyuk et al., 2016;Szwed, 2019;Fedoniuk et al., 2020) and other authors. In particular, a detailed analysis of such changes for the period 1985-2005, as well as a description of the trends observed was made for the period 1996-2013. For Ukrainian part of the region, presented in the monograph «Current ecological state and prospects for ecologically safe sustainable development of the Volyn region» (Fesyuk et al., 2016). According to (Fesyuk et al., 2016), since the end of the 80 s and 90 s of the 20 th century, there has been a tendency to increase the amount of precipitation in the region. Certainly, for the period 1986-2005 the average amount of precipitation for the territory of the Volyn region was determined to be within 609 mm (for the previous 10-year period, this amount was 601 mm). The ratio of precipitation amounts between the warm period of the year (70%) and the cold period (30%) was preserved.
Monthly amounts varied as follows: in winterfrom 39.1 mm in December to 32 mm in February, in summer from 74 mm in June to 65 mm in August. The monthly maximum was is July (83 mm). In autumn, the average monthly amounts decrease to 41-54 mm. According to data (Tarasyuk & Hanushchak, 2017, Fesyuk et al., 2016, during the late 20 th and early 21 st centuries average amounts of precipitation in the region were distributed as follows: the annual amount is 621 mm, the amount of precipitation for the warm period (April-October) is 435 mm, and the amount of precipitation for the cold period (November-March) is 186 mm.
According to estimates of mathematical modeling of regional climate processes in Ukraine, Poland, and in the Central European region as a whole, trends in the growth of precipitation amounts will persist in the study region, most forecasts do not foresee a significant decrease in the amount of precipitation (Krakovska et al., 2017;Zolina et al. al., 2014;Didovets et al., 2020).
The Volyn region is the «center» of the cross-border region Poland-Belarus-Ukraine, a typical subre-gion of this region, so let's analyze the dynamics of precipitation within its borders in more detail. Among the 6 Volyn meteorological stations, the largest annual amounts of precipitation were recorded in the 20 th and early 21 st centuries at the weather station (furtherstation) Manevychi (660 mm) and station Volodymyr (600 mm). The least amount of precipitation fell on st. Lutsk (552 mm) and st. Svityaz (561.5 mm). The average annual precipitation in Kovel was 593 mm, and in St. Liubeshiv -598 mm. During the historical period of observations, the lowest amount of precipitation was recorded in 1961 at St. Liubeshiv (270.3 mm), and the wettest was in 1998 (1001 mm according to Manevychi station) (Babichenko & Zuzuk, 1988, Fesyuk et al., 2016. Since the 80s, the region has experienced years without stable snow cover (up to 50% of years), while the winter of 1995-1996. was characterized by an abnormally long (148 days according to Liubeshiv) period of snow accumulation. In the period 1998-2010, according to (Tarasyuk and Hanushchak, 2017), a trend of increasing average monthly and average annual precipitation was noted. Significant growth was observed in August and early spring, in March-April. The station Manevychi continued to be the «wettest» in Volyn, although according to the station Lutsk, the positive dynamics of rainfall was particularly noticeable.
In general, the analyzed works note various regional manifestations of modern climatic changes, and, in particular, trends toward the growth of monthly and annual precipitation amounts. For separate successive periods, some researchers give the following values of average annual precipitation: 601 mm (first half of the 20th century), 609 mm , 621 mm (1996-2010) (Fesyuk et al., 2016;Melnik, Buyakov, Chernyshev, 2019).
At the same time, the analysis of changes in the frequency of precipitation (dynamics of the number of days with precipitation for certain periods), and changes in the dynamics of precipitation amounts between the seasons of the year. There was no detailed cartographic visualization of the latest dynamics of precipitation in the region or its individual subdistricts is not sufficiently presented in the scientific literature.
Despite considerable attention to this problem, most of the cited works represent the results of local research (within certain oblasts, districts of Ukraine, southern regions of the Republic of Belarus or eastern voivodships of Poland, within the Shatsky NPP or other nature conservation areas, etc.). Therefore, we consider it relevant to conduct such a comprehensive study for the territory of the cross-border region as a whole.

Materials and methods
The main source materials of the conducted research were archives of meteorological information available on the resources of the World Data Centers and the European Climate Assessment & Dataset (ECA&D) web service. All calculated indicators were compared with the data of the climatic norm (averaged values of meteorological indicators over a 30-year period, data from the period 1961-1990 were used). Indicators of the climatic norm for each meteorological station were searched both in literary sources, in the institutions of the hydrometeorological service of Ukraine and on specialized meteorological sites. The time period of 2010-2018 was chosen for the analysis, in particular, to establish the possible prerequisites for the severe dehydration of Polissya in 2019. At that time, a significant decrease in the levels of ground and underground water was observed, as well as the shallowing of many lakes. Among them, the historic minimum water levels of Lake Svityaz were recorded for the entire period of instrumental observations, which caused significant public and scientific resonance. (Fedoniuk et al., 2020). Since precipitation plays an important role in the formation of the hydrological regime of the territory and significantly affects landscape complexes, the analysis of their dynamics in the specified period is of scientific interest.
Calculations of the main indicators of the atmospheric precipitation regime were carried out based on the data of 17 meteorological stations located in the cross-border region Poland-Belarus-Ukraine, namely: stations Svityaz, Lutsk, Kovel, Liubeshiv, Manevychi, Volodymyr-Volynskyi (Volyn region, Ukraine, from 2021 -Volodymyr), Sarny, Dubno, Rivne (Rivne region, Ukraine), Brody, Rava-Ruska, Kamianka-Buzka (Lviv region, Ukraine), Pruzhany, Pinsk (Republic of Belarus), Terespol, Wlodawa, Zamosc (Republic of Poland) for the period 2010-2018. The selection of meteorological stations for the analysis of archival information was determined by: a) their geographical location within the study area; b) the completeness and reliability of the found archival information; c) the affinity of the climatic province and similar type of circulation processes; d) uniform coverage of observation points in the research region.
MS Excel tools were used in the process of statistical analysis of archival meteorological information. The spatial distribution of the calculated average annual precipitation amounts and average amounts for the warm and cold periods of the year will be displayed using the cartographic tools of the Gold-enSoftware Surfer software package (v.13.0) using kriging interpolation methods, local polynomials, and the radial basis function. A map of localized charts showing annual amounts of precipitation by weather stations was built in MapInfoPro (v.15.0).
With the help of statistical methods, for each of the 17 named meteorological stations, the following were calculated: average monthly amounts of precipitation, average amounts of precipitation for the warm period of the year (covering the IV-X months) and the cold period of the year (covering the XI-III months), and also determined the average amounts precipitation for each year and for the entire period under investigation. The number of days with precipitation per year, during the warm and cold periods, and its average values were also determined. All named indicators were also calculated as arithmetic averages between 17 stations. The processing of the results of the primary data arrays for each weather station made it possible to calculate the averaged and total values of the precipitation dynamics indicators, which are presented in Tables 1 and 2. Based on the obtained data, several graphs, diagrams and cartograms were constructed, which visually represent the peculiarities of the precipitation dynamics in the region during 2010-2018.

Results
The analysis of the average monthly amounts of precipitation according to the data of 17 meteorological stations in the cross-border region of Poland-Belarus-Ukraine showed that the average amounts of precipitation for the months of the year at the weather stations are increasing in comparison with the indicators of the climatic standard (Table 1). This growth fluctuates on average for the studied period within 5-15% of the annual norm of precipitation amounts. In some months and years, the growth is much higher and can reach 35-45% of the climatic standard. The greatest increase in annual precipitation amounts (up to 15% above the standard) was noted for Lutsk, Wlodawa, and Rava-Ruska stations. The smallest growth (less than 1-2%) is for Sarny and Rivne stations. The analysis of the summary diagram of the distribution of monthly amounts of precipitation during the year (Fig. 1) shows that a significant increase in the average monthly amounts of precipitation in the region is observed in January, March, April, and May. However, in some months of the year, on the contrary, a decrease in the average monthly amount of precipitation by 5-10% was noted in comparison with the indicators of the climatic standard (in February, August, November, in some years -in June and September). Although an increasing trend of the average annual amount of precipitation was recorded at 17 weather stations, in some years, annual amounts of precipitation that were significantly lower than the indicators of the climatic standard were recorded (for example, 2015 was so dry, see Table 2). In some years, the indicators of the climatic standard were exceeded by 1.2-1.5 times (for example, in 2010, 2012). Having analyzed the data presented in table 2 and diagrams in fig. 2, we can conclude that during 2010-2018, the average annual amount of precipitation increased at all weather stations, while the average annual number of days with precipitation during the year decreased.
The increase in the average annual amount of precipitation in the region varies from 6.2 mm (Rivne station) to 117.4 mm (Rava-Ruska station), for individual stations this increase is from 1% to 16% of the climatic norm. The greatest increase in the average annual amount of precipitation in comparison with the climatic standard was noted for the station Rava-Ruska (at 117.4 mm), station Lutsk (by 92.7 mm), station Wlodawa (by 65.2 mm). This growth was the smallest for sta. Level (by 6.2 mm), station Sarny (by 12.5 mm), station Manevychi (by 18.7 mm). In our opinion, the reasons for the uneven growth of precipitation amounts at individual stations in the region are the large territorial variability of this meteorological indicator as a whole. However, the geographical regularity of the distribution is also observed: the smallest increase in the amount of precipitation was observed at those of the 17 analyzed weather stations located further to the east of the region. Since the main mass of atmospheric precipitation in our region is of frontal origin, and the systems of atmospheric fronts are associated with cyclonic formations and move mainly from the west, southwest, and northwest to east, then such a distribution is natural. It should be noted that the station Rava-Ruska, for which the largest increase in the average annual amount of precipitation was noted, is generally characterized by the largest indicator of the climatic norm in terms of the annual amount of precipitation among the 17 analyzed stations.
The average increase in annual precipitation for the region during the period 2010-2018 was 46 mm. The obtained results are correlated with the studies of the authors, who analyzed the indicators of atmospheric precipitation for the territories that are part of the cross-border region Poland-Belarus-Ukraine or border with it, and also described the trends in the growth of average annual amounts of precipitation in recent decades (see the study (Fesyuk et al. ., 2016), which was carried out for the territory of the Volyn region of Ukraine and the work (Melnik, Buyakov, Chernyshev, 2019), in which an assessment of trends in changes in precipitation indicators within the territory of the Republic of Belarus is given.
At the same time, a decrease in the annual number of days with precipitation was noted at the vast majority of weather stations (14 out of 17). According to averaged data, this decrease amounted to 21 days for the region. The redistribution of the number of days with precipitation at different weather stations was quite uneven. The decrease in the average number of days with precipitation ranged from 56-40 days (Manevychi station, Kamianka-Buzka station, Svityaz station) to 8-15 days (Dubno, Pruzhany, Brody). On the contrary, a slight increase in the average number of days with precipitation was noted at three stations: the increase amounted to 9-13 days for the station. Wlodawa, Terespol, Zamosc. The geographical regularity of the location of points in which the number of days with precipitation increased during the year in the northwestern part of the study region is monitored.
Thus, the decrease in the number of days with precipitation during the year in the region is quite noticeable and amounts to 5-25% for individual stations and periods of the year. It can be assumed that certain single and daily precipitation amounts have also increased significantly in the region, but these indicators were not the subject of research in this work.  fig.  3-4 can show us that during the studied period, the amount of precipitation increased for both warm and cold periods of the year at the vast majority of weather stations. We can see a particularly significant increase in the sums of the warm period for the station Lutsk (76.7 mm), sta. Rava-Ruska (66.7 mm), sta. Wlodawa (37.8 mm) and sta. Svityaz (36.6 mm). In the cold pe-riod of the year, the amount of precipitation increased most significantly for sta. Rava-Ruska (50.7 mm), Pinsk (41.7 mm), sta. Brody and Liubeshiv (34.3 mm), this increase is noticeable also for the station Sarny (28.5 mm), sta. Wlodawa (27.4 mm), sta. Svityaz (24.6 mm). A comparison of the average amounts of precipitation falling during the warm and cold periods of the year with the indicators of the climatic standard shows that the distribution of these amounts by season has become more uniform. If, according to the data of the climatic norm, the ratio between the amounts of precipitation that fell in the warm and cold period of the year was characterized by indicators of 75/25%, then in the studied period this ratio is estimated to be within the range of 60/40%.

Analysis of table 2 and integrated diagrams in
It should be noted that the obtained results are correlated with the indicators of regional climate models.
Most of the modern models predict further preservation or a slight increase in the amount of precipitation in the region (Krakovska et al., 2017), (Kamyshenko, 2012.). At the same time, a change in the precipitation regime in combination with higher evaporation costs in the warm period of the year can contribute to a decrease of the territory in the water content and, as a result, to a decrease in the levels of groundwater and surface water bodies. Such a problem has repeatedly arisen in the Polissya zone in recent times and requires the search, development, and implementation of complex solutions for adaptation to climatic changes in farming technologies in sensitive industries. In fig. 5 presents a graphical interpretation of a separate, in-depth analysis of the dynamics of atmospheric precipitation for 6 Volyn meteorological stations of the studied region, the results of which were published, in particular, (Fedoniuk & Kostiv, 2018). The analysis of the integrated diagram in Fig.  5 allows us to say that during the studied years the amounts of precipitation have increased both for the warm and the cold period of the year. We can see a special increase in warm period amounts within the Volyn region for Lutsk, and cold period precipitation amounts for Liubeshiv.
Comparing the results of the analysis of the average annual amounts of precipitation in the warm and cold periods of the year according to the data of 17 weather stations of the cross-border region of Poland-Belarus-Ukraine and the Volyn region, in particular, we note that there is a tendency for the amounts of precipitation in the cold period to increase in the northern part of the study region, and in the western part the region has seen an increase in the amount of precipitation in both the warm and cold periods of the year.
Based on the calculated indicators, a cartogram of the dynamics of annual amounts of precipitation at 17 weather stations during the period 2010-2018 was constructed (Fig. 6), and a number of cartograms of the geographical distribution of atmospheric precipitation amounts in the studied territory during 2010.  The map diagram in Fig. 6 allows you to visualize significant fluctuations in the annual amount of precipitation, which are manifested even in such a relatively short period of time, which was chosen for the study. Analysis of table data 2 and the diagram in Fig.  6 allows you to note the abnormal dryness of 2015, which manifested itself in a sharp decrease in the amount of precipitation at all stations of the region. According to the data in Table 2, in 2015, the average annual amount of precipitation decreased by 20-30% in compared to the indicators of the climatic standard. The largest decrease was for the station Sarny (by 174 mm), sta. Svityaz and sta. Rivne (at 150-151 mm). In general, the higher aridity of the abnormal value for the period 2010-2018 in 2015 was noted in the north of the studied territory.
The Fig. 7 presents a cartogram of the average annual amounts of precipitation in the studied area.  fig. 7, shows the presence of an area with increased average annual precipitation, extending from the southwest, approximately along the line Rava-Ruska -Manevychi. The average annual isohyets in the studied area vary from 605 mm to 705 mm. The highest amounts of precipitation are for stations Rava-Ruska and Manevychi, and we note that the station Manevychi retains its status as the «rainiest» in Volyn, which was defined for it in classic scientific surveys, particularly, in works (Gerenchuk, 1975), (Babichenko & Zuzuk, 1988), (Zuzuk, 1988), (Chemerys, 2000). At the same time, there is a significant increase in the amount of precipitation in the Lutsk station in comparison with the indicators of the climatic norm, which can be explained by the influence of the city as a large «heat island» and a dynamic obstacle in the way of air masses in recent decades, when there was a massive development of the city's micro districts, an increase in the area of city blocks and the height of buildings in it.
Cartogram in fig. 8a, which represents the geographical distribution of average amounts of precipita-tion in the warm period of the year in the cross-border region of Poland-Belarus-Ukraine, is characterized by the same territorial differences in the distribution of precipitation as for the annual average. Isohyets change values from 495 mm to 385 mm, the zone of increased amounts of precipitation during the warm period of the year is outlined along the Rava-Ruska -Manevychi axis.
The geographical distribution of average amounts of precipitation in the cold period of the year, which is presented on the cartogram in fig. 8b, has its own peculiarities. A zone of reduced amounts of precipitation in the cold period of the year (with amounts less than 200 mm), located along the axis Terespol -Lutsk -Rivne, and two areas of higher values of the indicator (amounts of precipitation in the cold period over 200 mm) to the north and south of it are distinguished. We assume that this geographical distribution of precipitation amounts in the cold period of the year is related to the peculiarities of circulation processes and their changes over the studied area.
In general, according to the maps in fig. 7-8, the following trend can be traced: if in the summer and in general throughout the year the amount of precipitation decreases «classically», from west to east, then in the cold period the established rule is violated. We assume that this is related to changes in the circulation of air masses that occur during the transition from one season of the year to another, particularly, with the growing role of the meridional component in the circulation, as indicated by several researchers (Barabash et al., 2009;Meshyk & Valuev, 2005).

Сonclusions
Therefore, for the studied period of 2010-2018, a trend towards an increase in the annual amount of precipitation in the region and a decrease in the annual number of days with precipitation was revealed. Average annual amounts of precipitation increased at all 17 meteorological stations located in the cross-border region Poland-Belarus-Ukraine. This increase ranged from 5 to almost 120 mm/year at individual stations, on average it ranged from 35 to 45 mm. At the same time, the average annual number of days with precipitation decreased by 15-30% at most weather stations (14 out of 17). The dynamics of precipitation during the year has changed: the distribution of days with precipitation has become more uniform by season. If in the past the ratio between the amounts of precipitation that fell in the warm and cold period of the year was characterized by indicators of the ratio of 75/25, then in the studied period this ratio is within the limits of 60/40.
At 15 weather stations out of 17 studied, the average annual precipitation exceeded 600 mm in the analyzed period. The dynamics of precipitation amounts by month of the year is more complex and variable: there is both a sharp increase in monthly amounts (up to 50-80%) in some years, and their decrease (by 50-60%) in other periods. A tendency to increase the average monthly amounts of precipitation by 5-15% compared to the indicators of the climatic norm in January, March, April, and May was revealed. Average monthly amounts of precipitation decreased by 5-10% in February, August, November, in some years the decrease is typical for June and September).
Thus, one of the consequences of regional manifestations of climate change within the cross-border region of Poland-Belarus-Ukraine is a slight increase in the average annual amount of precipitation, a decrease in the number of days with precipitation during the year, and a significant change in their intra-annual dynamics. Accordingly, the amount of precipitation during the analyzed period is not the reason for the subsequent decrease in the water content of Polish ecosystems, but the mode of their precipitation may partially influence it.