Characterizing seasonal spatiotemporal rainfall dynamics through integrated analysis of precipitation concentration, trend detection, and change-point assessment

Rainfall is a fundamental component of hydrological systems, and its changing characteristics under a warming climate pose significant challenges for water security and climate adaptation. Despite receiving substantial annual precipitation, Bangladesh is increasingly exposed to rainfall uncertainty associated with changing seasonal distributions and long-term hydroclimatic shifts. This study aims to provide an integrated assessment of rainfall dynamics by examining precipitation concentration, long-term trends, and abrupt regime shifts. Forty years of rainfall records (1984-2023) from 25 meteorological stations were analyzed using the coefficient of variation (CV), precipitation concentration index (PCI), Mann-Kendall (MK) trend test, Sen’s slope estimator, and change-point detection methods. The key findings of this study are as follows: (1) Annual PCI analysis revealed irregular rainfall distribution, with the highest concentration at Teknaf (PCI = 21.52). (2) Trend analysis showed declining annual and monsoon rainfall, with the strongest decline at Madaripur (Z MK = −2.83, p < 0.005). (3) Change-point analysis identified abrupt rainfall regime shifts, particularly during the 1980s and recent decades. The spatially heterogeneous rainfall responses highlight the combined influence of monsoon variability, regional atmospheric processes, and coastal climatic controls. The findings provide evidence for climate adaptation and sustainable water-resource management in Bangladesh.