Characterization of heatwave pattern and its long-run predictions using CMIP6 model in western and north-western climatic zones of Bangladesh.

Heatwaves, characterized by prolonged high temperatures, have become a recurrent and severe phenomenon in Bangladesh, posing significant risks to public health, agriculture, and socioeconomic stability. This study analyzed the characterization and long-term projections of heatwave patterns in Bangladesh's western and northwestern climatic zones, addressing a critical gap in understanding regional vulnerabilities to extreme temperature events. Heatwave thresholds were defined using the Bangladesh Meteorological Department Criterion, a percentile-based criterion, and the Indian Meteorological Department Criterion, providing a comprehensive framework for assessing heatwave intensity and frequency. Using nine bias-corrected general circulation models from CMIP6 (Coupled Model Intercomparison Project Phase 6), the study examined historical heatwave patterns (1990-2014) across five cities, Bogra, Chuadanga, Dinajpur, Ishwardi, and Rajshahi, and evaluated future projections for three epochs: Epoch (2026-2050), Epoch (2051-2075), and Epoch (2076-2100). The findings revealed a significant increase in heatwave days under the high-emission Shared Socioeconomic Pathway (SSP ) scenario compared to SSP , with SSP projected to have 46.7% more heatwave days on average across the three epochs. The largest disparities are observed in Chuadanga (49.4%) and Rajshahi (44.5%), with Chuadanga emerging as the most vulnerable region, experiencing 1629 cumulative heatwave days under SSP in Epoch , compared to 1301 under SSP -a 25.2% increase. These findings underscore the profound impact of human activities on heatwave frequency and emphasize the urgent need for climate change mitigation. By offering a novel approach to heatwave characterization, this study provides critical insights to inform regional climate resilience planning and develop targeted adaptation measures.