Spatio-temporal rainfall variability and trends in northern part of Bangladesh: A statistical and GIS perspective

This study investigates long-term spatial and temporal rainfall homogeneity, variability, concentration, and trends across northern Bangladesh, a climate-sensitive region where rainfall variability has important implications for water resources and agriculture. Daily rainfall records from eight meteorological stations covering the 42-year period (1982-2023) were analysed. After homogeneity analyses, rainfall variability and concentration were quantified using the coefficient of variation (CV) and Precipitation Concentration Index (PCI), respectively. Trends were examined using the Mann-Kendall (MK), and Innovative Trend Analysis (ITA). Spatial patterns were characterized using inverse distance weighting (IDW). Rainfall records were largely homogeneous, with low-to-moderate annual and monsoon variability (CV: 20.72%, 23.81%) but extreme dry-season variability. PCI indicated uniform monsoon rainfall (8.99%-9.61%) and predominantly irregular annual rainfall. MK showed significant declines at 3 stations annually and 4 during monsoon, with Sen’s slopes of −14.08 to −7.11 and −13.89 to −8.60 mm/year, respectively. ITA identified increasing post-monsoon and pre-monsoon trends at 50% of stations. The study advances existing assessments by integrating rainfall homogeneity, variability, and trend-detection approaches. The relatively sparse station network may, however, limit the representation of fine-scale spatial rainfall variability. These findings provide useful evidence for improving rainfall monitoring and supporting climate-informed water-resource and agricultural planning in northern Bangladesh.