In hydrology, precipitation is the most critical variable and plays the most significant role in the hydrological cycle (Yang et al., 2020b). This variable also is a key factor in water resources management and weather-related studies. Due to adverse effects of climate change on the atmosphere, more intensified precipitation and severe droughts have happened, and precipitation patterns are changed in both spatial and temporal distributions (Cui et al., 2022; Kidd and Huffman, 2011; Papalexiou and Montanari, 2019). While in some regions, people and the environment experience more severe droughts and water shortages, in others, several floods and heavy precipitation events are occurring more than in the past (Donat et al., 2017; Guo et al., 2020). These abnormalities, including changes in the amount of precipitation, changes in frequency, time shifting, and concentration, have a considerable influence on social life and the ecosystem (Donat et al., 2017; Papalexiou and Montanari, 2019). Over earth's land, precipitation has risen by nearly 2% due to global warming, which could raise the water-holding capability of the atmosphere by approximately 7% per one-degree increment in temperature, which could intensify anomalies in the distribution of precipitation (Cui et al., 2022; Darand and Pazhoh, 2022). For example, due to mentioned changes, in Iran, semi-arid areas over 400 years have transformed into arid regions (Gholami et al., 2017).
Changes in precipitation patterns and the regime could increase concerns about water resources management plans and projections for sustainable developments. For example, temperature increments and precipitation pattern changes can significantly change the evaporation rates and soil moisture conditions in the growing season or water losses in large reservoirs or lakes (Cui et al., 2022; Pizarro et al., 2013). In this regard, Guo et al. (2020) investigated spatiotemporal changes in precipitation concentration and their effects on drought across China, and their results show that changes in precipitation patterns have different influences on drought events in China. Alternatively, Yang et al. (2020a) have shown that precipitation regime changes are closely related to teleconnection indices over Central Asia. Yang et al. (2020b) have identified that shifts from light to heavy rainfall could cause the risk of heavy floods and soil erosion and lead to substantial water resource management issues. Thus, it seems that investigations in precipitation spatiotemporal changes may help to increase the understanding of different aspects of the adverse effects of climate change over a region.
To identify changes in precipitation patterns, several indices and statistical methods are proposed and tested in different regions, such as Precipitation Concentration Index (PCI), Long-cycle Drought-Flood Abrupt alternation index (LDFAI), Precipitation Concentration Period (PCP), Multi-time scale mutual information entropy (MTSMIE), and Precipitation Concentration Degree (PCD) (Cortesi et al., 2012; Cui et al., 2022; Darand and Pazhoh, 2022; Li et al., 2011; Martin-Vide, 2004). Using these indices over Bangladesh, an abnormal trend in precipitation concentration was detected (Mondol et al., 2018). Over Europe, by employing these indices, it is noted that ocean/sea have primary effects on the spatial distribution of the concentration indicators (Cortesi et al., 2012). Darand and Pazhoh (2022) have identified that precipitation concentration is increased, and the frequency of the number of wet days is decreased in Iran. However, according to Cortesi et al. (2012), daily rainfall distribution has not substantially changed over Europe from 1971 to 2010. In addition, these methods help identify the effect of teleconnections indices on droughts and flood events (Xie et al., 2022; Yang et al., 2020a; Yin et al., 2021). However, in most of the studies, researchers have focused on the changes in the amount of precipitation and negative trends in precipitation over the regions, but spatiotemporal precipitation changes in many regions are still unknown (Yang et al., 2020a).
Based on the literature, Central Europe is one of the regions where several droughts and floods have happened during the past decades and caused several socio-economic issues (Gvoždíková and Müller, 2017; Hisdal et al., 2001; Ionita et al., 2021; Mudelsee et al., 2003). These hazards are mainly linked to changes in precipitation; however, anthropogenic changes could intensify these problems (Boergens et al., 2020; Bryndal, 2015; Kundzewicz et al., 2005). In addition, in the north of this region, the Baltic Sea is located, and according to its characteristics, this sea is sensitive to droughts, and low flows could affect the quality of the Baltic Sea and its ecosystem (Babre et al., 2022; Kundzewicz, 2009; Meier et al., 2012; Rutgersson et al., 2022).
The motivation of this study is the lack of analyses on precipitation concentration in Central Europe, while several studies have investigated the trends in the study area (Ziernicka-Wojtaszek and Kopcińska, 2020). The novelty of this study is the first comprehensive evaluation of the precipitation concentration variability by employing various indicators over a region in Central Europe. This study aims to evaluate precipitation concentration indicators and periods of occurrence and their trends using a high-resolution, regional precipitation data set. The outcomes of this study could improve understanding of the effect of changes in precipitation concentration on regional drought monitoring, soil erosion and land conservation and alterations.