Statistical Analysis and Indicators of Climatic Instability of Atmospheric Precipitation in the Ternopil Region (1969-2024)

Atmospheric precipitation is a fundamental climatic parameter that determines the hydrological regime, water resource availability, and agricultural potential of the Podillia Upland. Under the conditions of global thermal transformation, the Ternopil region experiences significant changes in its moisture patterns. The traditional approach of analyzing only mean annual values is becoming less effective for climate risk assessment. Therefore, identifying indicators of climatic instability and analyzing the amplitude of moisture extremes ("climatic swings") is a highly relevant scientific task. The study is based on a 55-year homogeneous series of instrumental observations (1969-2024) from four representative meteorological stations: Kremenets (North), Ternopil (Center), Berezhany (West), and Chortkiv (South). The methodological framework includes mathematical-statistical analysis (standard deviation, coefficient of variation), the cumulative sum method (CUSUM) for trend detection, and the newly introduced Climate Contrast Index ($CI$). This index calculates the relative amplitude between the upper and lower quartiles of annual precipitation totals, providing a robust measure of regional climatic destabilization. The research confirms a pronounced spatial asymmetry in the precipitation field. The highest climatic norm is recorded in the North (Kremenets – 695 mm), driven by the orographic barrier effect of the Kremenets Hills, while the central part (Ternopil – 579 mm) remains the most conservative. A critical finding is the intensification of "climatic swings" – the increasing amplitude between extreme dry and wet years. The maximum instability was identified in the West (Berezhany), where the annual precipitation range reached a record 675 mm (from 1083 mm in 1980 to 408 mm in 2015). The calculated Climate Contrast Index (CI) demonstrated the highest values for Berezhany (0.32) and Chortkiv (0.29), signaling an increased sensitivity of these areas to atmospheric circulation shifts. The intra-annual distribution analysis reveals a hazardous shift in the precipitation structure during the warm season (April-October). Despite these months accounting for 65-70% of the annual total, the transition toward a discrete-convective (storm-based) regime reduces the effective moisture security. In the 2000-2024 period, August precipitation exhibited a 14-fold difference between the absolute minimum (11 mm) and maximum (160 mm). Such extreme variability leads to "apparent moisture security," where intense rainfall generates rapid surface runoff and soil erosion without replenishing deep groundwater or productive soil moisture. Cumulative sum analysis (CUSUM) identified a strategic "break point" around the year 2000, marking the beginning of a steady accumulation of negative moisture anomalies across the region. The modern climate of the Ternopil region is transforming toward a state of chronic instability. This is manifested not in a linear decrease of total precipitation, but in the expansion of the "climatic corridor" between droughts and floods. These findings are essential for developing regional adaptation strategies, particularly for implementing moisture-conserving agricultural technologies and managing hydrological risks in the Dniester River basin. The proposed indicators of instability (amplitude and CI index) should be integrated into the regional climate monitoring system to enhance the predictability of hydrometeorological hazards.