Characterization of Long-Term Annual and Seasonal Rainfall Trends in Coastal Areas of Bangladesh

Abstract

Abstract Bangladesh has a highly vulnerable 710 km long low-lying coastline with over 29% of the country’s population residing in coastal districts. While existing literature examines inland rainfall patterns, analysis of rainfall variability along the coast is lacking. This study analyzes annual and seasonal rainfall trends across 17 coastal meteorological stations over 1948–2021. The non-parametric Mann-Kendall test and Sen’s Slope estimator are applied for trend detection and quantification. The findings reveal high interannual and spatial rainfall variability across stations, governed primarily by monsoonal dynamics. A seasonal analysis shows noticeable winter rainfall increases at Khulna and Satkhira at rates of 0.38 mm/year and 0.32 mm/year respectively. The critical monsoon months exhibit substantial incremental tendencies at Khepupara (11.77 mm/year), Hatiya (10.54 mm/year) and Kutubdia (15.50 mm/year). Additionally, post-monsoon rainfall rises significantly at Hatiya (5.25 mm/year). For annual totals, significant rising trends are observed at Khulna (7.69 mm/year), Khepupara (16.43 mm/year), Hatiya (21 mm/year) and Sandwip (12.45 mm/year). Across the seasonal and annual timescales, widespread non-significant increasing tendencies dominate over declining behaviors for most stations. This study provides key inputs for planning and policies to build climate resilience of vulnerable coastal populations.